How can I efficiently split and execute large MySQL files within a PHP environment without overloading memory?

Importing MySQL Files in PHP: Splitting Queries Effectively

When importing large MySQL files into a PHP-powered website, it's crucial to handle queries efficiently. Without access to the MySQL command line, splitting a file into single queries becomes essential.

Memory-Friendly Solution

The following function splits a large SQL file into individual queries without requiring the entire file to be loaded into memory:

<code class="php">function SplitSQL($file, $delimiter = ';')
{
    set_time_limit(0);

    if (is_file($file) === true)
    {
        $file = fopen($file, 'r');

        if (is_resource($file) === true)
        {
            $query = array();

            while (feof($file) === false)
            {
                $query[] = fgets($file);

                if (preg_match('~' . preg_quote($delimiter, '~') . '\s*$~iS', end($query)) === 1)
                {
                    $query = trim(implode('', $query));

                    if (mysql_query($query) === false)
                    {
                        echo '<h3>ERROR: ' . $query . '</h3>' . "\n";
                    }

                    else
                    {
                        echo '<h3>SUCCESS: ' . $query . '</h3>' . "\n";
                    }

                    while (ob_get_level() > 0)
                    {
                        ob_end_flush();
                    }

                    flush();
                }

                if (is_string($query) === true)
                {
                    $query = array();
                }
            }

            return fclose($file);
        }
    }

    return false;
}</code>

This function addresses common gotchas such as field delimiters and line breaks in memo fields.

Test Data and Output

To demonstrate the function's effectiveness, consider the following test data:

<code class="sql">CREATE TABLE IF NOT EXISTS "test" (
    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
    "name" TEXT,
    "description" TEXT
);

BEGIN;
    INSERT INTO "test" ("name", "description")
    VALUES (";;;", "something for you mind; body; soul");
COMMIT;

UPDATE "test"
    SET "name" = "; "
    WHERE "id" = 1;</code>

Executing the SplitSQL function on this data produces the following output:

SUCCESS: CREATE TABLE IF NOT EXISTS "test" ( "id" INTEGER PRIMARY KEY AUTOINCREMENT, "name" TEXT, "description" TEXT );
SUCCESS: BEGIN;
SUCCESS: INSERT INTO "test" ("name", "description") VALUES (";;;", "something for you mind; body; soul");
SUCCESS: COMMIT;
SUCCESS: UPDATE "test" SET "name" = "; " WHERE "id" = 1;

This demonstrates the reliability of the function in splitting queries accurately.

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