How to Convert Camel Case to Snake Case in PHP ?

Given a Camel Case String, the task is to convert the Camel Case String to a Snake Case String in PHP.

Examples:

Input: GeeksForGeeks
Output: geeks_for_geeks

Input: WelcomeToGfg 
Output: welcome_to_gfg

Camel case uses capital letters at the beginning of each word except the first one, while snake case separates words with underscores and uses all lowercase letters.

Approach 1: Using Manual Conversion

The simplest way to convert camel case to snake case is to do it manually by iterating through each character of the string and inserting an underscore before each capital letter.

PHP

<?php

function camelToSnake($camelCase) {
    $result = '';

    for ($i = 0; $i < strlen($camelCase); $i++) {
        $char = $camelCase[$i];

        if (ctype_upper($char)) {
            $result .= '_' . strtolower($char);
        } else {
            $result .= $char;
        }
    }

    return ltrim($result, '_');
}

// Driver code
$camelCase = 'WelcomeToGeeksForGeeks';
$snakeCase = camelToSnake($camelCase);
echo $snakeCase;

?>

Output

welcome_to_geeks_for_geeks

Approach 2: Using Regular Expressions

Regular expressions provide a concise way to achieve the conversion from camel case to snake case.

PHP

<?php

function camelToSnake($camelCase) {
    $pattern = '/(?<=\\w)(?=[A-Z])|(?<=[a-z])(?=[0-9])/';
    $snakeCase = preg_replace($pattern, '_', $camelCase);
    return strtolower($snakeCase);
}

// Driver code
$camelCase = 'WelcomeToGeeksForGeeks';
$snakeCase = camelToSnake($camelCase);

echo $snakeCase;

?>

Output

welcome_to_geeks_for_geeks