switch_theme( string $stylesheet )

Description

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$stylesheetstring

Stylesheet name.

Performance profile

How much work a call to switch_theme() 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

Heavy

Reaches the database via ->delete().

Scaling

Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions

113–180

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 206.

Plugin surface

1 hook

Third-party callbacks on 'switch_theme' run inside this call, and their cost is not bounded by anything here.

Called by

9

9 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• optionoption read or writeupdate_option()called directly
• hookthird-party callbacksdo_action()called directly
• sqldatabase query->delete()called directly
• serializeserialisationmaybe_serialize()one call below switch_theme()
• cacheobject cachewp_cache_get()one call below switch_theme()

Further down the call graph this can also reach 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 · 1912 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost switch_theme() can have, taken from its control-flow graph on PHP 8.5.