php mysql首先检查db

<?php
$thesite = strip_tags($_GET['s']);

$original_file = @file_get_contents($thesite);
if ($original_file  === false) {
    die("$thesite does not exist");
} elseif($orginial_file === true ) {
    $data = $path_info['host'];
    $check = mysql_query("SELECT * FROM first WHERE name='$data'");
} else {
    //step3
}

I want to check the DB for $data. If it exists, move on to the next step; if not, do step 3

<?php

$thesite = strip_tags($_GET['s']);

$original_file = @file_get_contents($thesite);
if ($original_file  === false) {
    die("$thesite does not exist");
} elseif($orginial_file === true ) {
    $data = $path_info['host'];
    $check = mysql_query("SELECT * FROM first WHERE name='$data'");
    #exist = mysql_num_rows($check);
    if ($exist) {
        // next step
    }
    else {
        // step 3
    }
}

Check the value of mysql_num_rows after running the query. If it's 0, there were no rows with name equal to $data.

By the way, you shouldn't be inserting $data directly into your query, otherwise you're open to SQL injection. Here's a better way:

mysql_query("SELECT * FROM first WHERE name='".mysql_real_escape_string($data)."'");

Also, file_get_contents will not return true if it succeeds. It will return the contents of the file as a string.