Source

File: wp-includes/functions.php

function wp_raise_memory_limit( $context = 'admin' ) {
	// Exit early if the limit cannot be changed.
	if ( false === wp_is_ini_value_changeable( 'memory_limit' ) ) {
		return false;
	}

	$current_limit     = ini_get( 'memory_limit' );
	$current_limit_int = wp_convert_hr_to_bytes( $current_limit );

	if ( -1 === $current_limit_int ) {
		return false;
	}

	$wp_max_limit     = WP_MAX_MEMORY_LIMIT;
	$wp_max_limit_int = wp_convert_hr_to_bytes( $wp_max_limit );
	$filtered_limit   = $wp_max_limit;

	switch ( $context ) {
		case 'admin':
			/**
			 * Filters the maximum memory limit available for administration screens.
			 *
			 * This only applies to administrators, who may require more memory for tasks
			 * like updates. Memory limits when processing images (uploaded or edited by
			 * users of any role) are handled separately.
			 *
			 * The `WP_MAX_MEMORY_LIMIT` constant specifically defines the maximum memory
			 * limit available when in the administration back end. The default is 256M
			 * (256 megabytes of memory) or the original `memory_limit` php.ini value if
			 * this is higher.
			 *
			 * @since 3.0.0
			 * @since 4.6.0 The default now takes the original `memory_limit` into account.
			 *
			 * @param int|string $filtered_limit The maximum WordPress memory limit. Accepts an integer
			 *                                   (bytes), or a shorthand string notation, such as '256M'.
			 */
			$filtered_limit = apply_filters( 'admin_memory_limit', $filtered_limit );
			break;

		case 'image':
			/**
			 * Filters the memory limit allocated for image manipulation.
			 *
			 * @since 3.5.0
			 * @since 4.6.0 The default now takes the original `memory_limit` into account.
			 *
			 * @param int|string $filtered_limit Maximum memory limit to allocate for images.
			 *                                   Default `WP_MAX_MEMORY_LIMIT` or the original
			 *                                   php.ini `memory_limit`, whichever is higher.
			 *                                   Accepts an integer (bytes), or a shorthand string
			 *                                   notation, such as '256M'.
			 */
			$filtered_limit = apply_filters( 'image_memory_limit', $filtered_limit );
			break;

		default:
			/**
			 * Filters the memory limit allocated for arbitrary contexts.
			 *
			 * The dynamic portion of the hook name, `$context`, refers to an arbitrary
			 * context passed on calling the function. This allows for plugins to define
			 * their own contexts for raising the memory limit.
			 *
			 * @since 4.6.0
			 *
			 * @param int|string $filtered_limit Maximum memory limit to allocate for images.
			 *                                   Default '256M' or the original php.ini `memory_limit`,
			 *                                   whichever is higher. Accepts an integer (bytes), or a
			 *                                   shorthand string notation, such as '256M'.
			 */
			$filtered_limit = apply_filters( "{$context}_memory_limit", $filtered_limit );
			break;
	}

	$filtered_limit_int = wp_convert_hr_to_bytes( $filtered_limit );

	if ( -1 === $filtered_limit_int || ( $filtered_limit_int > $wp_max_limit_int && $filtered_limit_int > $current_limit_int ) ) {
		if ( false !== ini_set( 'memory_limit', $filtered_limit ) ) {
			return $filtered_limit;
		} else {
			return false;
		}
	} elseif ( -1 === $wp_max_limit_int || $wp_max_limit_int > $current_limit_int ) {
		if ( false !== ini_set( 'memory_limit', $wp_max_limit ) ) {
			return $wp_max_limit;
		} else {
			return false;
		}
	}

	return false;
}