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WordPress

POMO_Reader::substr( string $input_string, int $start, int $length ): string

Source
wp-includes/pomo/streams.php:93

Compatibility

WordPress
core
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.

Parameters

$input_stringstring
$startint
$lengthint

Return value

string

Performance profile

How much work a call to POMO_Reader::substr() 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

Touches nothing outside its own arguments.

Scaling
Constant

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

Instructions
8–12

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 15.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
1

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

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 POMO_Reader::substr() can have, taken from its control-flow graph on PHP 8.5.

WhenInstructionsCalls it makes
always8none
always12mb_substr()

Across PHP versions

PHPCompiledExecutedBranchesNotes
8.6-dev158–121
8.5158–121
8.4158–1213 fewer instructions than PHP 8.3
8.31811–121
8.21811–121
8.11811–121
7.41811–121

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 · 1

Used by · 1

Source code

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		public function substr( $input_string, $start, $length ) {			if ( $this->is_overloaded ) {				return mb_substr( $input_string, $start, $length, 'ascii' );			} else {				return substr( $input_string, $start, $length );			}		}

Changelog

Unchanged from 6.7.7 through 7.1.0.

  1. 6.7.7
  2. 6.8.8
  3. 6.9.7
  4. 7.0.4
  5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data
Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/pomo/streams.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
Corrections
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