<?php

    set_time_limit(0); // for bigger databases

    $host = '';
    $user = '';
    $pass = '';
    $dbname = '';

    $new_collation = 'utf8_general_ci';

    $convert_string = 'convert(cast(convert(%s using  latin1) as binary) using utf8)';
    $alter_table_and_all_columns = 'alter table %s convert to character set utf8 collate '.$new_collation;

    $conn = mysqli_connect($host,$user,$pass,$dbname);

    $sql = "SHOW TABLES";
    $result = mysqli_query($conn,$sql);

    while($row = mysqli_fetch_assoc($result)) {
        $table_list[] = $row['Tables_in_'.$dbname];
    }

    foreach($table_list as $table) {
        $res = mysqli_query($conn,"SHOW CREATE TABLE $table");

        $row = mysqli_fetch_array($res);

        #echo $row[0] . "<br>\n";

        $foo = mysqli_query($conn, "SHOW FULL  COLUMNS FROM $table");

        $set = [];

        while ($row1 = mysqli_fetch_array($foo)) {
            if (!empty($row1['Collation'])) {
                # echo $row1['Field'] . ' ' . $row1['Collation'] . "\n";
                $set[] = $row1['Field'];
            }
        }

        $sql1 = "UPDATE $table SET ";

        $sets = [];

        foreach($set as $field) {
            $sets[] = $field.'='.sprintf($convert_string,$field);
        }
        $sql1 .= implode(",",$sets);
        $res1 = mysqli_query($conn,$sql1);

        if (preg_match('#CHARSET=latin1#msi', $row[1])) {
            $res2 = mysqli_query($conn, sprintf($alter_table_and_all_columns, $table));
        }
    }