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I've installed Wordpress under ArchLinux on my VPS, configured the SQL backend and edited /usr/share/webapps/wordpress/wp-config.php. Unfortunately on trying to access pages I'm getting...

2019/06/14 06:44:12 [error] 20812#20812: *394 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Error: Call to undefined function mysql_connect() in /usr/share/webapps/wordpress/wp-includes/wp-db.php:1645 Stack trace: #0 /usr/share/webapps/wordpress/wp-includes/wp-db.php(639): wpdb->db_connect() #1 /usr/share/webapps/wordpress/wp-includes/load.php(427): wpdb->__construct('wp-user', 'pc&0wC<k%:o<AuI...', 'wordpress', 'localhost') #2 /usr/share/webapps/wordpress/wp-settings.php(120): require_wp_db() #3 /usr/share/webapps/wordpress/wp-config.php(90): require_once('/usr/share/weba...') #4 /usr/share/webapps/wordpress/wp-load.php(37): require_once('/usr/share/weba...') #5 /usr/share/webapps/wordpress/wp-blog-header.php(13): require_once('/usr/share/weba...') #6 /usr/share/webapps/wordpress/index.php(17): require('/usr/share/weba...') #7 {main} thrown in /usr/share/webapps/wordpress/wp-includes/wp-db.php on line 1645" while reading response header from upstream, client:...

Searching around this appears to happen under PHP when its attempting to use the mysql module rather than mysqli (found threads here and here).

I've enabled mysqli in /etc/php/php.ini

extension=mysqli

...and the module is loaded...

php -m [PHP Modules] Core ctype curl date dom fileinfo filter hash json libxml mbstring mysqli mysqlnd openssl pcntl pcre PDO Phar posix readline Reflection session SimpleXML SPL standard tokenizer xml xmlreader xmlwriter zip zlib [Zend Modules]

Reading through /usr/share/webapps/wordpress/wp-includes/wp-db.php around the offending line (1645) it looks to me as though there are a series of if{} else{} statements starting on line 1589 which checks to see if use_mysqli is being used,this fails and as there is no mysql module in they was removed in PHP7 and mysqli should instead be used.

grep '\$this->use_mysqli' /usr/share/webapps/wordpress/wp-includes/wp-db.php -A100 -n | grep 1589 -A100 1589: if ( $this->use_mysqli ) { 1590- $this->dbh = mysqli_init(); 1591- 1592- $host = $this->dbhost; 1593- $port = null; 1594- $socket = null; 1595- $is_ipv6 = false; 1596- 1597- if ( $host_data = $this->parse_db_host( $this->dbhost ) ) { 1598- list( $host, $port, $socket, $is_ipv6 ) = $host_data; 1599- } 1600- 1601- /* 1602- * If using the `mysqlnd` library, the IPv6 address needs to be 1603- * enclosed in square brackets, whereas it doesn't while using the 1604- * `libmysqlclient` library. 1605- * @see https://bugs.php.net/bug.php?id=67563 1606- */ 1607- if ( $is_ipv6 && extension_loaded( 'mysqlnd' ) ) { 1608- $host = "[$host]"; 1609- } 1610- 1611- if ( WP_DEBUG ) { 1612- mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags ); 1613- } else { 1614- @mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags ); 1615- } 1616- 1617- if ( $this->dbh->connect_errno ) { 1618- $this->dbh = null; 1619- 1620- /* 1621- * It's possible ext/mysqli is misconfigured. Fall back to ext/mysql if: 1622- * - We haven't previously connected, and 1623- * - WP_USE_EXT_MYSQL isn't set to false, and 1624- * - ext/mysql is loaded. 1625- */ 1626- $attempt_fallback = true; 1627- 1628- if ( $this->has_connected ) { 1629- $attempt_fallback = false; 1630- } elseif ( defined( 'WP_USE_EXT_MYSQL' ) && ! WP_USE_EXT_MYSQL ) { 1631- $attempt_fallback = false; 1632- } elseif ( ! function_exists( 'mysql_connect' ) ) { 1633- $attempt_fallback = false; 1634- } 1635- 1636- if ( $attempt_fallback ) { 1637: $this->use_mysqli = false; 1638- return $this->db_connect( $allow_bail ); 1639- } 1640- } 1641- } else { 1642- if ( WP_DEBUG ) { 1643- $this->dbh = mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags ); 1644- } else { 1645- $this->dbh = @mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags ); 1646- } 1647- }

This fails because, looking further back through /usr/share/webapps/wordpress/wp-includes/wp-db.php I can see $is_mysql is set to null on line 564 and $use_mysqli is set to false which explains why the test to see if use_mysqli is being used fails and instead connect_mysql() is being attempted...

grep 'public \$is_mysql = null' /usr/share/webapps/wordpress/wp-includes/wp-db.php -A30 -n 564: public $is_mysql = null; 565- 566- /** 567- * A list of incompatible SQL modes. 568- * 569- * @since 3.9.0 570- * @var array 571- */ 572- protected $incompatible_modes = array( 573- 'NO_ZERO_DATE', 574- 'ONLY_FULL_GROUP_BY', 575- 'STRICT_TRANS_TABLES', 576- 'STRICT_ALL_TABLES', 577- 'TRADITIONAL', 578- ); 579- 580- /** 581- * Whether to use mysqli over mysql. 582- * 583- * @since 3.9.0 584- * @var bool 585- */ 586- private $use_mysqli = false;

Given mysql has been removed since PHP7 and is not a listed possible module in /etc/php/php.ini I'm surprised $use_mysqli = false on a fresh install. I've tried setting it to true and after restarting php-fpm.service now get another error and enter the if ( $this->$use_mysqli){...} section only to fail on the first call to $this->dbh = mysqli_init()...

2019/06/14 07:10:25 [error] 1439#1439: *1 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Error: Call to undefined function mysqli_init() in /usr/share/webapps/wordpress/wp-includes/wp-db.php:1591 Stack trace: #0 /usr/share/webapps/wordpress/wp-includes/wp-db.php(640): wpdb->db_connect() #1 /usr/share/webapps/wordpress/wp-includes/load.php(427): wpdb->__construct('wp-user', 'pc&0wC<k%:o<AuI...', 'wordpress', 'localhost') #2 /usr/share/webapps/wordpress/wp-settings.php(120): require_wp_db() #3 /usr/share/webapps/wordpress/wp-config.php(90): require_once('/usr/share/weba...') #4 /usr/share/webapps/wordpress/wp-load.php(37): require_once('/usr/share/weba...') #5 /usr/share/webapps/wordpress/wp-blog-header.php(13): require_once('/usr/share/weba...') #6 /usr/share/webapps/wordpress/index.php(17): require('/usr/share/weba...') #7 {main} thrown in /usr/share/webapps/wordpress/wp-includes/wp-db.php on line 1591" while reading response header from upstream, client:

I'm not adverse to modifying configuration but the impression I had from Arch Wiki : Wordpress article is that this level of tinkering is not required. Can anyone advise on where I might have gone wrong.

EDIT

mysqli section from phpinfo()

mysqli MysqlI Support enabled Client API library version mysqlnd 5.0.12-dev - 20150407 - $Id: 7cc7cc96e675f6d72e5cf0f267f48e167c2abb23 $ Active Persistent Links 0 Inactive Persistent Links 0 Active Links 0 Directive Local Value Master Value mysqli.allow_local_infile Off Off mysqli.allow_persistent On On mysqli.default_host no value no value mysqli.default_port 3306 3306 mysqli.default_pw no value no value mysqli.default_socket /run/mysqld/mysqld.sock /run/mysqld/mysqld.sock mysqli.default_user no value no value mysqli.max_links Unlimited Unlimited mysqli.max_persistent Unlimited Unlimited mysqli.reconnect Off Off mysqli.rollback_on_cached_plink Off Off

EDIT2 : Its suggested that php-fpm wasn't loading the mysqli module, I've now checked and it appears to...

$ php-fpm -m [PHP Modules] cgi-fcgi Core ctype curl date dom fileinfo filter hash json libxml mbstring mysqli mysqlnd openssl pcntl pcre PDO pdo_mysql Phar posix readline Reflection session SimpleXML SPL standard tokenizer xml xmlreader xmlwriter zip zlib [Zend Modules]
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3 Answers 3

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2

You are right, meddling like this should not be necessary. A quick grep shows that $use_mysqli is set in line 621 in wp-db.php:

 // Use ext/mysqli if it exists unless WP_USE_EXT_MYSQL is defined as true if ( function_exists( 'mysqli_connect' ) ) { $this->use_mysqli = true; if ( defined( 'WP_USE_EXT_MYSQL' ) ) { $this->use_mysqli = ! WP_USE_EXT_MYSQL; } }

So, for some reason WordPress can't find the function mysqli_connect().

Please make sure that the mysqli module is loaded for the webserver. The command php -m only confirms that it is loaded for the command line interface, which may use a different configuration file. You can create a php file with phpinfo() to check this. Don't forget to restart your Apache after enabling the mysqli module in PHP.

If it is loaded and you still encounter the error, you can set the variable WP_USE_EXT_MYSQL to false to force WordPress to use mysqli. You only need to add this to your wp_config.php:

define("WP_USE_EXT_MYSQL", false);
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  • Thanks for the quick response, phpinfo() here shows the configure has '--with-mysqli=shared,mysqlnd' and further down there is a section for mysqli showing directives mysqli_connect is not listed there. I've restarted php-fpm.service and nginx.service but still get Error establishing a database connection returned and now nothing in /var/log/nginx/error.log (although /var/log/nginx/access.log records attempts to view page). Commented Jun 14, 2019 at 12:52
  • The output of your phpinfo() confirms that the mysqli module is not loaded. There should be a section with that name that shows some of the mysqli options. Find the correct configuration file of your php-fpm (The package summary shows some files and directories named php-fpm in /etc/php/) and enable it. Commented Jun 14, 2019 at 13:04
  • I found a section headed mysqli although many of the values are Null (/no value). Is enabling mysqli under /etc/php/php-fpm.conf the same as for /etc/php/php.conf as I've done above, i.e. just adding extension=mysqli? EDIT : Its not I added the line and it fails to start, off to read php-fpm configuration Commented Jun 14, 2019 at 13:15
  • I've tried adding echo 'extension=mysqli' > /etc/php/conf.d/mysql.ini but that doesn't work either. Commented Jun 14, 2019 at 13:23
  • Ok, I've checked and php-fpm -m (output added above) lists mysqli, mysqlnd and pdo_mysql as modules that are used. This is the default as I've removed the /etc/php/conf.d/mysql.ini that I created. Commented Jun 15, 2019 at 8:35
0

I've resolved this and the underlying problem was the password for the backend mariadb/mysql.

Wasn't at all clear from the logs which reported...

PHP message: PHP Fatal error: Uncaught Error: Call to undefined function mysqli_init() in /usr/share/webapps/wordpress/wp-includes/wp-db.php:1591

However, I started stripping things back and after checking mariadb.service was running tried connecting to it as the wp-user with the existing password from the command line and this failed. Changing the password allowed me to connect at the command line and complete the configuration of /usr/share/webapps/wordpress/wp-config.php. \o/

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sudo apt-get install php7.4-mysql sudo service apache2 restart
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  • Thanks although as I wrote in the opening I'm using ArchLinux and not Debian/Debian based distro and have already solved it as I posted, it was a password issue to the MariaDB for the wp-user. Commented Feb 26, 2021 at 10:38

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