wp_post_preview_js()
- Since
- 4.3.0
- Source
wp-includes/functions.php:7731
window.name when a user is navigating to another page.Description
This prevents reusing the same tab for a preview when the user has navigated away.
Compatibility
- WordPress
- since 4.3.0
- 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 wp_post_preview_js() 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
- 5–23
- 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, depending on the branch taken. The body compiles to 24.
Nothing here hands control to plugin code.
Nothing in core calls this; the cost is only what you spend yourself.
What one call costs · 2 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost wp_post_preview_js() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 5–7 | is_preview() |
is_preview() && !empty($post) | 23 | is_preview(), ob_start(), ob_get_clean(), wp_remove_surrounding_empty_script_tags(), wp_print_inline_script_tag() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 24 instructions, 5–23 executed per call, 2 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 · 3
- is_preview()Determines whether the query is for a post or page preview.
- wp_print_inline_script_tag()Prints an inline script tag.
- wp_remove_surrounding_empty_script_tags()Removes leading and trailing _empty_ script tags.
Source code
function wp_post_preview_js() { global $post; if ( ! is_preview() || empty( $post ) ) { return; } // Has to match the window name used in post_submit_meta_box(). $name = 'wp-preview-' . (int) $post->ID; ob_start(); ?> <script> ( function() { var query = document.location.search; if ( query && query.indexOf( 'preview=true' ) !== -1 ) { window.name = '<?php echo $name; ?>'; } if ( window.addEventListener ) { window.addEventListener( 'pagehide', function() { window.name = ''; } ); } }()); </script> <?php wp_print_inline_script_tag( wp_remove_surrounding_empty_script_tags( ob_get_clean() ) );}Changelog
Introduced in 4.3.0. 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-includes/functions.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.