compression_test()
- Since
- 2.8.0
- Source
wp-admin/includes/template.php:2483
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.
Compatibility
- WordPress
- since 2.8.0
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Performance profile
How much work a call to compression_test() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Trivial
- Scaling
- Constant
- Instructions
- 10
- Plugin surface
- None
- Called by
- 0
Touches nothing outside its own arguments.
No loop in the body: the same number of instructions runs whatever you pass in.
Executed per call on PHP 8.5. The body compiles to 10.
Nothing here hands control to plugin code.
Nothing in core calls this; the cost is only what you spend yourself.
What it touches
- hookthird-party callbacks
apply_filters()one call below compression_test()
Further down the call graph this can also reach option, cache, serialize, transient and query. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.
What one call costs · 1 distinct outcome
One number would be a lie: the work depends on which branch runs. These are every distinct cost compression_test() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 10 | wp_create_nonce(), wp_json_encode() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 10 instructions, 10 executed per call, 0 branches. The work does not change between versions.
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Uses · 2
- wp_json_encode()Encodes a variable into JSON, with some confidence checks.
- wp_create_nonce()Creates a cryptographic token tied to a specific action, user, user session, and window of time.
Source code
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}Changelog
Introduced in 2.8.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 6.7.7 tag, from
src/wp-admin/includes/template.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.