# 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

### 说明

public 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.

### 参数

`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:

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

### 返回值

成功时返回 `true`， 或者在失败时返回 `false`。

### 示例

示例 #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";
}
?>`

以上示例会输出：

    a1
    a10
    a2

    a1
    a2
    a10

### 参见

- Pdo\Sqlite::createFunction() - Registers a user-defined function for use in SQL statements
- Pdo\Sqlite::createAggregate() - Registers an aggregating user-defined function for use in SQL statements
- sqlite_create_function()
- sqlite_create_aggregate()

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