Pdo\Sqlite::createCollation

(PHP 8 >= 8.4.0)

Pdo\Sqlite::createCollation — Registers a user-defined function for use as a collating function in SQL statements

Description

public function Pdo\Sqlite::createCollation(string $name, callable $callback): bool

This method is similar to Pdo\Sqlite::createFunction() except that it registers functions that are used to collate strings.

Parameters

name

Name of the SQL collating function to be created or redefined.

callback

Callback function that defines the behaviour of a collation. It must accept two strings and return -1, 0, or 1 if the first string sorts before, sorts identically, or sorts after the second string respectively. An internal function that behaves like this is strcmp().

This function need to be defined as:

function collation(string $string1, string $string2): int

Return Values

Returns true on success or false on failure.

Errors/Exceptions

A TypeError is thrown if the callback does not return an int.

Changelog

Version Description
8.4.0 A TypeError is now thrown if the callback does not return an int; previously the returned value was cast to int.

Examples

Example #1 Pdo\Sqlite::createCollation() example

<?php
$db = new Pdo\Sqlite('sqlite::memory:');
$db->exec("CREATE TABLE test (col1 string)");
$db->exec("INSERT INTO test VALUES ('a1')");
$db->exec("INSERT INTO test VALUES ('a10')");
$db->exec("INSERT INTO test VALUES ('a2')");

$db->sqliteCreateCollation('NATURAL_CMP', 'strnatcmp');
foreach ($db->query("SELECT col1 FROM test ORDER BY col1") as $row) {
  echo $row['col1'] . "\n";
}
echo "\n";
foreach ($db->query("SELECT col1 FROM test ORDER BY col1 COLLATE NATURAL_CMP") as $row) {
  echo $row['col1'] . "\n";
}
?>

The above example will output:

a1
a10
a2

a1
a2
a10

See Also

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