mpdf error - preg_replace(): The /e modifier is deprecated, use preg_replace_callback instead

Try replacing lines 79 and 80 of functions.php with this:

$str = preg_replace_callback('/\&\#([0-9]+)\;/m', function($m) use ($lo){return code2utf($m[1],$lo); }, $str);$str = preg_replace_callback('/\&\#x([0-9a-fA-F]+)\;/m', function($m) use ($lo){return codeHex2utf($m[1],$lo);}, $str);

Source: https://github.com/carlholmberg/mpdf/issues/1

$str = preg_replace('/\&\#([0-9]+)\;/me', "code2utf('\\1',{$lo})",$str);$str = preg_replace('/\&\#x([0-9a-fA-F]+)\;/me', "codeHex2utf('\\1',{$lo})",$str);// Remove above and add below code in includes/functions.php$str = preg_replace_callback('/\&\#([0-9]+)\;/m', function($m) use ($lo){return code2utf($m[1],$lo); }, $str);$str = preg_replace_callback('/\&\#x([0-9a-fA-F]+)\;/m', function($m) use ($lo){return codeHex2utf($m[1],$lo);}, $str);// Also comment below line in mpdf.php$html = preg_replace('/\{DATE\s+(.*?)\}/e',"date('\\1')",$html );

$str = preg_replace('/\&\#([0-9]+)\;/me', "code2utf('\\1',{$lo})",$str);$str = preg_replace('/\&\#x([0-9a-fA-F]+)\;/me', "codeHex2utf('\\1',{$lo})",$str);// Remove above and add below code in includes/functions.php$str = preg_replace_callback('/\&\#([0-9]+)\;/m', function($m) use ($lo){return code2utf($m[1],$lo); }, $str);$str = preg_replace_callback('/\&\#x([0-9a-fA-F]+)\;/m', function($m) use ($lo){return codeHex2utf($m[1],$lo);}, $str);// Also comment below line in mpdf.php$html = preg_replace('/\{DATE\s+(.*?)\}/e',"date('\\1')",$html );