PHP comes with a vast library of built-in functions that you can use for various purposes, ranging from string manipulation, array handling, file operations, session management, and much more. Here’s an overview of some of the categories of built-in functions in PHP, along with examples from each category:
| Name | Description |
|---|---|
| error_log | Send an error message to the defined error handling routines |
| Category | Function | Description |
|---|---|---|
| String Functions | ||
| String | strlen($string) | Returns the length of a string. |
| str_replace($search, $replace, $subject) | Replaces all occurrences of the search string with the replacement string. | |
| strpos($haystack, $needle) | Finds the position of the first occurrence of a substring in a string. | |
| Array Functions | ||
| Array | array_merge($array1, $array2) | Merges one or more arrays. |
| count($array) | Counts all elements in an array, or something in an object. | |
| array_filter($array, $callback) | Filters elements of an array using a callback function. | |
| File System Functions | ||
| File System | fopen($filename, $mode) | Opens file or URL. |
| file_get_contents($filename) | Reads entire file into a string. | |
| file_put_contents($filename, $data) | Write data to a file. | |
