In PHP, functions are blocks of reusable code that perform specific tasks. Below is a comprehensive list of built-in PHP functions categorized by their general purpose:
PHP Functions Overview
1. String Functions
strlen(): Get the length of a string.strpos(): Find the position of the first occurrence of a substring in a string.str_replace(): Replace all occurrences of a search string with a replacement string.strtoupper(): Convert a string to uppercase.strtolower(): Convert a string to lowercase.ucfirst(): Capitalize the first character of a string.trim(): Strip whitespace (or other characters) from the beginning and end of a string.substr(): Return part of a string.explode(): Split a string by a string delimiter.implode(): Join array elements into a string.
2. Array Functions
count(): Count the elements in an array.array_merge(): Merge one or more arrays.array_diff(): Compute the difference of arrays.array_slice(): Extract a slice of an array.in_array(): Check if a value exists in an array.array_keys(): Return all the keys of an array.array_values(): Return all the values of an array.array_map(): Apply a callback to the elements of an array.array_filter(): Filter elements of an array using a callback function.
3. Mathematical Functions
abs(): Get the absolute value.round(): Round a floating-point number.floor(): Rounds down to the nearest integer.ceil(): Rounds up to the nearest integer.rand(): Generate a random integer.max(): Find the highest value in an array or list of values.min(): Find the lowest value in an array or list of values.
4. Date and Time Functions
date(): Format a local date and time.strtotime(): Parse an English textual datetime description into a Unix timestamp.time(): Return the current Unix timestamp.mktime(): Get the Unix timestamp for a date.date_diff(): Calculate the difference between two DateTime objects.
5. File Handling Functions
fopen(): Open a file or URL.fclose(): Close an open file pointer.fread(): Read from a file.fwrite(): Write data to a file.file_get_contents(): Get the contents of a file into a string.file_exists(): Check whether a file or directory exists.unlink(): Delete a file.
6. Error Handling Functions
error_reporting(): Set the level of error reporting.set_error_handler(): Sets a user-defined error handler function.trigger_error(): Generates a user-level error/warning/notice.
7. Variable Handling Functions
isset(): Determine if a variable is set and is not NULL.empty(): Determine whether a variable is empty.unset(): Unset a variable.
8. Type Casting and Conversion Functions
(int): Cast a variable to an integer.(float): Cast a variable to a float.(string): Cast a variable to a string.(array): Cast a variable to an array.(object): Cast a variable to an object.
9. Session Functions
session_start(): Start a new session or resume an existing session.session_destroy(): Destroy all data registered to a session.$_SESSION: Superglobal array to store session variables.
10. JSON Functions
json_encode(): Returns a JSON representation of a value.json_decode(): Decodes a JSON string.
11. Miscellaneous Functions
gettype(): Returns the type of a variable.var_dump(): Dumps information about a variable.die(): Output a message and terminate the current script.exit(): Output a message and terminate the current script.
12. Network Functions
curl_init(): Initialize a cURL session.curl_setopt(): Set an option for a cURL transfer.curl_exec(): Execute a cURL session.curl_close(): Close a cURL session.
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