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compression_test()

Test support for compressing JavaScript from PHP

Description

Outputs JavaScript that tests if compression from PHP works as expected and sets an option with the result. Has no effect when the current user is not an administrator. To run the test again the option ‘can_compress_scripts’ has to be deleted.

Source

File: wp-admin/includes/template.php 

function compression_test() {
	?>
	<script type="text/javascript">
	var compressionNonce = <?php echo wp_json_encode( wp_create_nonce( 'update_can_compress_scripts' ) ); ?>;
	var testCompression = {
		get : function(test) {
			var x;
			if ( window.XMLHttpRequest ) {
				x = new XMLHttpRequest();
			} else {
				try{x=new ActiveXObject('Msxml2.XMLHTTP');}catch(e){try{x=new ActiveXObject('Microsoft.XMLHTTP');}catch(e){};}
			}

			if (x) {
				x.onreadystatechange = function() {
					var r, h;
					if ( x.readyState == 4 ) {
						r = x.responseText.substr(0, 18);
						h = x.getResponseHeader('Content-Encoding');
						testCompression.check(r, h, test);
					}
				};

				x.open('GET', ajaxurl + '?action=wp-compression-test&test='+test+'&_ajax_nonce='+compressionNonce+'&'+(new Date()).getTime(), true);
				x.send('');
			}
		},

		check : function(r, h, test) {
			if ( ! r && ! test )
				this.get(1);

			if ( 1 == test ) {
				if ( h && ( h.match(/deflate/i) || h.match(/gzip/i) ) )
					this.get('no');
				else
					this.get(2);

				return;
			}

			if ( 2 == test ) {
				if ( '"wpCompressionTest' === r )
					this.get('yes');
				else
					this.get('no');
			}
		}
	};
	testCompression.check();
	</script>
	<?php
}

Uses

Uses Description
wp-includes/functions.php: wp_json_encode()

Encode a variable into JSON, with some sanity checks.
wp-includes/pluggable.php: wp_create_nonce()

Creates a cryptographic token tied to a specific action, user, user session, and window of time.

Changelog

Version Description
2.8.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/compression_test