install.php mysql INNODB helper code

install.php

<?php
// found in: ci-build/wordpress-tests-lib/includes/install.php
// reference: https://core.trac.wordpress.org/ticket/34692

/**
 * Shell function that returns the version of mysql regardless of using PDO or MySQLi
 * @return string - the numbered version of mysql i.e 5.7.14
 */
function get_mysql_version() {
  $output = shell_exec('mysql -V');
  preg_match('@[0-9]+\.[0-9]+\.[0-9]+@', $output, $version);

  if ( is_array( $version ) ) {
  	return $version[0]; 
  }

  return;
}


// Use PDO if enabled otherwise fallback to mysqli check
$mysql_version = get_mysql_version();


// Perform version comparing to decide what storage engine string should be used.
if ( isset( $mysql_version ) ) {
	
		$mysql_version = explode( '.', $mysql_version );
		
		if ( is_array( $mysql_version ) ) {
			// We know that mysql version 5.7+ use default_storage_engine so match the first two numbers
			// and ensure that it is equal to or greater than 5.7
			if ( (int) $mysql_version[0] >= 5 && (int) $mysql_version[1] >= 7 ) {
				$wpdb->query( 'SET default_storage_engine = INNODB' );
			} else {
				$wpdb->query( 'SET storage_engine = INNODB' );
			}
		} else {
			// fallback when $mysql_version is not set as an array
			$wpdb->query( 'SET storage_engine = INNODB' );	
		}
} else {
	// Load as fallback
	$wpdb->query( 'SET storage_engine = INNODB' );
}