Second pair of eyes, why is the query failing to execute.

Think I'm missing something here. I can print/echo the $sql variable and paste it into phpMyadmin and it works just fine, but for some reason it will not work correctly here. Anybody see anything off?

Thank you

<?php
///Write Text File To Local Database
//declare variables
$i='1';
$handle= fopen('inventory.txt','r');
$sql='';
$find='"';
$replace='';
$first='';
$second='';
///read file
while(!feof($handle)) {
    $gets = fgets($handle,4096);
    list($first,$second)=explode(',',$gets);
    //create sql
    $sql.="INSERT INTO facts_inventory (`part_number`,`facts_qty_on_hand`)
    VALUES ('".trim(str_replace($find,$replace,$first))."','".trim(str_replace($find,$replace,$second))."')
    ON DUPLICATE KEY UPDATE
    `facts_qty_on_hand` = '".trim(str_replace($find,$replace,$second))."';";
    $i++;
}
    if(mysql_query($sql)) {
        ///it Worked
        echo 'Updated '.$i.' fields.';
    } else {
        //Query Failed
    echo "<br>Failed at executing sql query. ";
    }
?>