PHP Cheat Sheet, Cheat Sheet of Computer Science

Download PHP Cheat Sheet and more Cheat Sheet Computer Science in PDF only on Docsity! Beginner’s essential PHP Cheat Sheet Fast, flexible and pragmatic scripting language. ################# TABLE OF CONTENTS PHP Basics 3 Variables and Constants 3 PHP Arrays – Grouped Values 8 PHP Strings 13 PHP Operators 20 Loops in PHP 22 Conditional Statements 23 Working with Forms in PHP 24 PHP Filters 25 HTTP Functions in PHP 27 Working with MySQL 28 Date and Time 32 PHP Errors 36 of 2 38 $_SERVER 
 Contains information about the locations of headers, paths and scripts $_GET 
 Can collect data that was sent in the URL or submitted in an HTML form $_POST 
 Used to gather data from an HTML form and to pass variables $_REQUEST 
 Also collects data after submitting an HTML form Variable-handling Functions boolval 
 Used to retrieve the boolean value of a variable debug_zval_dump 
 Outputs a string representation of an internal zend value empty 
 Checks whether a variable is empty or not floatval 
 Get the float value of a variable (doubleval is another possibility) get_defined_vars 
 Returns an array of all defined variables get_resource_type 
 Returns the resource type gettype 
 Retrieves the variable type import_request_variables 
 Import GET/POST/Cookie variables into the global scope intval 
 Find the integer value of a variable is_array 
 Checks whether a variable is an array is_bool 
 Finds out if a variable is a boolean of 5 38 is_callable 
 Verify whether you can call the contents of a variable as a function is_countable 
 Check whether the contents of a variable are countable is_float 
 Find out if the type of a variable is float, alternatives: is_double and is_real is_int 
 Check if the type of a variable is an integer, is_integer and is_long also works is_iterable 
 Verify that a variable’s content is an iterable value is_null 
 Checks whether a variable’s value is NULL is_numeric 
 Find out if a variable is a number or a numeric string is_object 
 Determines whether a variable is an object is_resource 
 Check if a variable is a resource is_scalar 
 Tests if a variable is a scalar is_string 
 Find out whether the type of a variable is a string isset 
 Determine if a variable has been set and is not NULL print_r 
 Provides human-readable information about a variable serialize 
 Generates a representation of a value that is storable settype 
 Sets a variable’s type strval 
 Retrieves the string value of a variable of 6 38 unserialize 
 Creates a PHP value from a stored representation unset 
 Unsets a variable var_dump 
 Dumps information about a variable var_export 
 Outputs or returns a string representation of a variable that can be parsed Constants define(name, value, true/false) Aside from user-defined constants, there also a number of default PHP constants: __LINE__ 
 Denotes the number of the current line in a file __FILE__ 
 Is the full path and filename of the file __DIR__ 
 The directory of the file __FUNCTION__ 
 Name of the function __CLASS__ 
 Class name, includes the namespace it was declared in __TRAIT__ 
 The trait name, also includes the namespace __METHOD__ 
 The class method name __NAMESPACE__ 
 Name of the current namespace of 7 38 array_pad 
 Inserts a specified number of items (with a specified value) into an array array_pop 
 Deletes an element from the end of an array array_product 
 Calculate the product of all values in an array array_push 
 Push one or several elements to the end of the array array_rand 
 Pick one or more random entries out of an array array_reduce 
 Reduce the array to a single string using a user-defined function array_replace 
 Replaces elements in the first array with values from following arrays array_replace_recursive 
 Recursively replaces elements from later arrays into the first array array_reverse 
 Returns an array in reverse order array_search 
 Searches the array for a given value and returns the first key if successful array_shift 
 Shifts an element from the beginning of an array array_slice 
 Extracts a slice of an array array_splice 
 Removes a portion of the array and replaces it array_sum 
 Calculate the sum of the values in an array array_udiff 
 Compare arrays and return the difference using a user function (values only) of 10 38 array_udiff_assoc 
 Compare arrays and return the difference using a default and a user function (keys and values) array_udiff_uassoc 
 Compare arrays and return the difference using two user functions (values and keys) array_uintersect 
 Compare arrays and return the matches via user function (values only) array_uintersect_assoc 
 Compare arrays and return the matches via a default user function (keys and values) array_uintersect_uassoc 
 Compare arrays and return the matches via two user functions (keys and values) array_unique 
 Removes duplicate values from an array array_unshift 
 Adds one or more elements to the beginning of an array array_values 
 Returns all values of an array array_walk 
 Applies a user function to every element in an array array_walk_recursive 
 Recursively applies a user function to every element of an array arsort 
 Sorts an associative array in descending order according to the value asort 
 Sorts an associative array in ascending order according to the value compact 
 Create an array containing variables and their values count 
 Count all elements in an array, alternatively use sizeof current 
 Returns the current element in an array, an alternative is pos of 11 38 each 
 Return the current key and value pair from an array end 
 Set the internal pointer to the last element of an array extract 
 Import variables from an array into the current symbol table in_array 
 Checks if a value exists in an array key 
 Fetches a key from an array krsort 
 Sorts an associative array by key in reverse order ksort 
 Sorts an associative array by key list 
 Assigns variables as if they were an array natcasesort 
 Sorts an array using a “natural order” algorithm independent of case natsort 
 Sorts an array using a “natural order” algorithm next 
 Advance the internal pointer of an array prev 
 Move the internal array pointer backwards range 
 Creates an array from a range of elements reset 
 Set the internal array pointer to its first element rsort 
 Sort an array in reverse order shuffle 
 Shuffle an array sort 
 Sorts an indexed array in ascending order of 12 38 echo() 
 Outputs one or several strings explode() 
 Breaks down a string into an array fprintf() 
 Writes a formatted string to a specified output stream get_html_translation_table() 
 Returns the translation table used by htmlspecialchars() and htmlentities() hebrev() 
 Transforms Hebrew text to visual text hebrevc() 
 Converts Hebrew text to visual text and implements HTML line breaks hex2bin() 
 Translate hexadecimal values to ASCII characters html_entity_decode() 
 Turns HTML entities to characters htmlentities() 
 Converts characters to HTML entities htmlspecialchars_decode() 
 Transforms special HTML entities to characters htmlspecialchars() 
 Switches predefined characters to HTML entities implode() 
 Retrieves a string from the elements of an array, same as join() lcfirst() 
 Changes a string’s first character to lowercase levenshtein() 
 Calculates the Levenshtein distance between two strings localeconv() 
 Returns information about numeric and monetary formatting for the locale ltrim() 
 Removes spaces or other characters from the left side of a string of 15 38 md5() 
 Calculates the MD5 hash of a string and returns it md5_file() 
 Calculates the MD5 hash of a file metaphone() 
 Provides the metaphone key of a string money_format() 
 Returns a string as a currency string nl_langinfo() 
 Gives specific locale information nl2br() 
 Inserts HTML line breaks for each new line in a string number_format() 
 Formats a number including grouped thousands ord() 
 Returns the ASCII value of a string’s first character parse_str() 
 Parses a string into variables print() 
 Outputs one or several strings printf() 
 Outputs a formatted string quoted_printable_decode() 
 Converts a quoted-printable string to 8-bit binary quoted_printable_encode() 
 Goes from 8-bit string to a quoted-printable string quotemeta() 
 Returns a string with a backslash before metacharacters rtrim() 
 Strips whitespace or other characters from the right side of a string setlocale() 
 Sets locale information sha1() 
 Calculates a string’s SHA-1 hash of 16 38 sha1_file() 
 Does the same for a file similar_text() 
 Determines the similarity between two strings soundex() 
 Calculates the soundex key of a string sprintf() 
 Returns a formatted string sscanf() 
 Parses input from a string according to a specified format str_getcsv() 
 Parses a CSV string into an array str_ireplace() 
 Replaces specified characters in a string with specified replacements (case-insensitive) str_pad() 
 Pads a string to a specified length str_repeat() 
 Repeats a string a preset number of times str_replace() 
 Replaces specified characters in a string (case-sensitive) str_rot13() 
 Performs ROT13 encoding on a string str_shuffle() 
 Randomly shuffles the characters in a string str_split() 
 Splits strings into arrays str_word_count() 
 Returns the number of words in a string strcasecmp() 
 Case-insensitive comparison of two strings strcmp() 
 Binary safe string comparison (case sensitive) of 17 38 ucwords() 
 Converts the first character of every word in a string to uppercase vfprintf() 
 Writes a formatted string to a specified output stream vprintf() 
 Outputs a formatted string vsprintf() 
 Writes a formatted string to a variable wordwrap() 
 Shortens a string to a given number of characters PHP OPERATORS Arithmetic Operators + — Addition - — Subtraction * — Multiplication / — Division % — Modulo (the remainder of value divided by another) ** — Exponentiation Assignment Operators += — a += b is the same as a = a + b -= — a -= b is the same as a = a – b *= — a *= b is the same as a = a * b /= — a /= b is the same as a = a / b %= — a %= b is the same as a = a % b Comparison Operators == — Equal of 20 38 === — Identical != — Not equal <> — Not equal !== — Not identical < — Less than > — Greater than <= — Less than or equal to >= — Greater than or equal to <=> — Less than, equal to, or greater than Logical Operators and — And or — Or xor — Exclusive or ! — Not && — And || — Or Bitwise Operators & — And | — Or (inclusive or) ^ — Xor (exclusive or) ~ — Not << — Shift left >> — Shift right of 21 38 Error Control Operator You can use the @ sign to prevent expressions from generating error messages. This is often important for security reasons, for example to keep confidential information safe. Execution Operator PHP supports one execution operator, which is `` (backticks). These are not single-quotes! PHP will attempt to execute the contents of the backticks as a shell command. Increment/Decrement Operators ++$v — Increments a variable by one, then returns it $v++ — Returns a variable, then increments it by one --$v — Decrements the variable by one, returns it afterward $v-- — Returns the variable then decrements it by one String Operators . — Used to concatenate (mean combine) arguments .= — Used to append the argument on the right to the left-side argument LOOPS IN PHP For Loop for (starting counter value; ending counter value; increment by which to increase) { // code to execute goes here } Foreach Loop foreach ($InsertYourArrayName as $value) { // code to execute goes here of 22 38 The advantage of this is that you’re able to bookmark the information. Keep in mind that it also means that the information is visible to everyone. For that reason, GET is not suitable for sensitive information such as passwords. It also limits the amount of data that can be sent in ca 2000 characters. POST, on the other hand, uses the HTTP POST method to pass on variables. This makes the data invisible to third parties, as it is sent in the HTTP body. You are not able to bookmark it. With POST, there are no limits to the amount of information you can send. Aside from that, it also has advanced functionality and is therefore preferred by developers. Form Security PHP offers tools to thwart those attacks, namely: htmlspecialchars() trim() stripslashes() Required Fields, Error Messages and Data Validation Aside from that, PHP is able to define required fields (you can’t submit the form without filling them out), display error messages if some information is missing and to validate data. We have already talked about the necessary tools to do so. For example, you can simply define variables for your form fields and use the empty() function to check if they have values. After that, create a simple if/else statement to either send the submitted data or output an error message. The next step is to check submitted data for validity. For that, PHP offers a number of filters such as FILTER_VALIDATE_EMAIL to make sure a submitted email address has the right format. PHP FILTERS Filter Functions filter_has_var() 
 Checks if a variable of the specified type exists of 25 38 filter_id() 
 Returns the ID belonging to a named filter filter_input() 
 Retrieves a specified external variable by name and optionally filters it filter_input_array() 
 Pulls external variables and optionally filters them filter_list() 
 Returns a list of all supported filters filter_var_array() 
 Gets multiple variables and optionally filters them filter_var() 
 Filters a variable with a specified filter Filter Constants FILTER_VALIDATE_BOOLEAN 
 Validates a boolean FILTER_VALIDATE_EMAIL 
 Certifies an e-mail address FILTER_VALIDATE_FLOAT 
 Confirms a float FILTER_VALIDATE_INT 
 Verifies an integer FILTER_VALIDATE_IP 
 Validates an IP address FILTER_VALIDATE_REGEXP 
 Confirms a regular expression FILTER_VALIDATE_URL 
 Validates a URL FILTER_SANITIZE_EMAIL 
 Removes all illegal characters from an e-mail address FILTER_SANITIZE_ENCODED 
 Removes/Encodes special characters of 26 38 FILTER_SANITIZE_MAGIC_QUOTES 
 Applies addslashes() FILTER_SANITIZE_NUMBER_FLOAT 
 Removes all characters, except digits, +- and .,eE FILTER_SANITIZE_NUMBER_INT
 Gets rid of all characters except digits and + – FILTER_SANITIZE_SPECIAL_CHARS 
 Removes special characters FILTER_SANITIZE_FULL_SPECIAL_CHARS 
 Converts special characters to HTML entities FILTER_SANITIZE_STRING 
 Removes tags/special characters from a string, alternative: FILTER_SANITIZE_STRIPPED FILTER_SANITIZE_URL 
 Rids all illegal characters from a URL FILTER_UNSAFE_RAW 
 Do nothing, optionally strip/encode special characters FILTER_CALLBACK 
 Call a user-defined function to filter data HTTP FUNCTIONS IN PHP HTTP Functions header() 
 Sends a raw HTTP header to the browser headers_list() 
 A list of response headers ready to send (or already sent) headers_sent() 
 Checks if and where the HTTP headers have been sent setcookie() 
 Defines a cookie to be sent along with the rest of the HTTP headers setrawcookie() 
 Defines a cookie (without URL encoding) to be sent along of 27 38 mysqli_get_client_version() 
 The MySQL client library version as an integer mysqli_get_connection_stats() 
 Statistics about the client connection mysqli_get_host_info() 
 The MySQL server hostname and the connection type mysqli_get_proto_info() 
 The MySQL protocol version mysqli_get_server_info() 
 Returns the MySQL server version mysqli_get_server_version() 
 The MySQL server version as an integer mysqli_info() 
 Returns information about the most recently executed query mysqli_init() 
 Initializes MySQLi and returns a resource for use with mysqli_real_connect() mysqli_insert_id() 
 Returns the auto-generated ID used in the last query mysqli_kill() 
 Asks the server to kill a MySQL thread mysqli_more_results() 
 Checks if there are more results from a multi query mysqli_multi_query() 
 Performs one or more queries on the database mysqli_next_result() 
 Prepares the next result set from mysqli_multi_query() mysqli_num_fields() 
 The number of fields in a result set mysqli_num_rows() 
 The number of rows in a result set mysqli_options() 
 Sets extra connect options and affect behavior for a connection of 30 38 mysqli_ping() 
 Pings a server connection or tries to reconnect if it has gone down mysqli_prepare() 
 Prepares an SQL statement for execution mysqli_query() 
 Performs a query against the database mysqli_real_connect() 
 Opens a new connection to the MySQL server mysqli_real_escape_string() 
 Escapes special characters in a string for use in an SQL statement mysqli_real_query() 
 Executes an SQL query mysqli_reap_async_query() 
 Returns the result from async query mysqli_refresh() 
 Refreshes tables or caches or resets the replication server information mysqli_rollback() 
 Rolls back the current transaction for the database mysqli_select_db() 
 Changes the default database for the connection mysqli_set_charset() 
 Sets the default client character set mysqli_set_local_infile_default() 
 Unsets a user-defined handler for the LOAD LOCAL INFILE command mysqli_set_local_infile_handler() 
 Sets a callback function for the LOAD DATA LOCAL INFILE command mysqli_sqlstate() 
 Returns the SQLSTATE error code for the last MySQL operation mysqli_ssl_set() 
 Establishes secure connections using SSL mysqli_stat() 
 The current system status of 31 38 mysqli_stmt_init() 
 Initializes a statement and returns an object for use with mysqli_stmt_prepare() mysqli_store_result() 
 Transfers a result set from the last query mysqli_thread_id() 
 The thread ID for the current connection mysqli_thread_safe() 
 Returns if the client library is compiled as thread-safe mysqli_use_result() 
 Initiates the retrieval of a result set from the last query executed using the mysqli_real_query() mysqli_warning_count() 
 The number of warnings from the last query in the connection DATE AND TIME Date/Time Functions checkdate() 
 Checks the validity of a Gregorian date date_add() 
 Adds a number of days, months, years, hours, minutes and seconds to a date object date_create_from_format() 
 Returns a formatted DateTime object date_create() 
 Creates a new DateTime object date_date_set() 
 Sets a new date date_default_timezone_get() 
 Returns the default timezone used by all functions date_default_timezone_set() 
 Sets the default timezone date_diff() 
 Calculates the difference between two dates of 32 38 timezone_identifiers_list() 
 An indexed array with all timezone identifiers timezone_location_get() 
 Location information for a specified timezone timezone_name_from_abbr() 
 Returns the timezone name from an abbreviation timezone_name_get() 
 The name of the timezone timezone_offset_get() 
 The timezone offset from GMT timezone_open() 
 Creates a new DateTimeZone object timezone_transitions_get()
 Returns all transitions for the timezone timezone_version_get() 
 Returns the version of the timezonedb Date and Time Formatting d — 01 to 31 j — 1 to 31 D — Mon through Sun l — Sunday through Saturday N — 1 (for Mon) through 7 (for Sat) w — 0 (for Sun) through 6 (for Sat) m — Months, 01 through 12 n — Months, 1 through 12 F — January through December M — Jan through Dec Y — Four digits year (e.g. 2018) y — Two digits year (e.g. 18) of 35 38 L — Defines whether it’s a leap year (1 or 0) a — am and pm A — AM and PM g — Hours 1 through 12 h — Hours 01 through 12 G — Hours 0 through 23 H — Hours 00 through 23 i — Minutes 00 to 59 s — Seconds 00 to 59 PHP ERRORS Error Functions debug_backtrace() 
 Used to generate a backtrace debug_print_backtrace() 
 Prints a backtrace error_get_last() 
 Gets the last error that occurred error_log() 
 Sends an error message to the web server’s log, a file or a mail account error_reporting() 
 Specifies which PHP errors are reported restore_error_handler() 
 Reverts to the previous error handler function restore_exception_handler() 
 Goes back to the previous exception handler set_error_handler() 
 Sets a user-defined function to handle script errors of 36 38 set_exception_handler() 
 Sets an exception handler function defined by the user trigger_error() 
 Generates a user-level error message, you can also use user_error() Error Constants E_ERROR 
 Fatal run-time errors that cause the halting of the script and can’t be recovered from E_WARNING 
 Non-fatal run-time errors, execution of the script continues E_PARSE 
 Compile-time parse errors, should only be generated by the parser E_NOTICE 
 Run-time notices that indicate a possible error E_CORE_ERROR 
 Fatal errors at PHP initialization, like an E_ERROR in PHP core E_CORE_WARNING 
 Non-fatal errors at PHP startup, similar to E_WARNING but in PHP core E_COMPILE_ERROR 
 Fatal compile-time errors generated by the Zend Scripting Engine E_COMPILE_WARNING 
 Non-fatal compile-time errors by the Zend Scripting Engine E_USER_ERROR 
 Fatal user-generated error, set by the programmer using trigger_error() E_USER_WARNING 
 Non-fatal user-generated warning E_USER_NOTICE 
 User-generated notice by trigger_error() E_STRICT 
 Suggestions by PHP to improve your code (needs to be enabled) E_RECOVERABLE_ERROR 
 Catchable fatal error caught by a user-defined handle of 37 38