gistfile1.php

<?php

$mysql_hostname = 'localhost';
$mysql_username = 'your_mysql_username';
$mysql_password = 'your_mysql_password';
$database       = 'your_mysql_database';
$table          = 'your_mysql_table' ;

$con = new mysqli($mysql_hostname, $mysql_username, $mysql_password, $database);

if ($con->connect_error) {
    die($con->connect_error);
} 

$i = 0;
while ($i <= 20000) {
    /* 
     * Use $randomString for varchars and texts and $randomInteger for integers and
     * real values.
    */
    $randomString  = substr(str_shuffle('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'), 0, $length);
    $randomInteger = rand(1000, 5500); 
    
    $sql_query = "INSERT INTO $table (column1, column2) VALUES ('$randomString', '$randomInteger')";  

    if ($con->query($sql_query) === TRUE)
        echo $i.' record added successfully.';
    else 
        echo $i.' th record could not be added: '. $con->error;
    
    $i = $i + 1;
}

$con->close();
?>