Ajax call timing out in certain circumstances? - php

Question

<?php
include_once '../includes/db_connect.php';
fetch_evt_values($conn, 7475, 2, 16);
function fetch_evt_values($conn, $p_frm_id, $p_evt_id, $p_usr_id) {
$p_rec_id = 0;
$l_rslt_msg = '';
$l_result = array(
'data' => array(),
'msg' => '0000'
);
$sql = 'BEGIN PHPEVT.EV_MOD.FETCH_EVT_VALUES(';
//$sql .= ':c_load_id,';
$sql .= ':c_frm_id,';
$sql .= ':c_evt_id,';
$sql .= ':c_rec_id,';
$sql .= ':c_usr_id,';
$sql .= ':c_rslt';
$sql .= '); END;';
if ($stmt = oci_parse($conn,$sql)) {
$l_results = oci_new_cursor($conn);
//oci_bind_by_name($stmt,':c_load_id',$p_load_id);
oci_bind_by_name($stmt,':c_frm_id',$p_frm_id);
oci_bind_by_name($stmt,':c_evt_id',$p_evt_id);
oci_bind_by_name($stmt,':c_rec_id',$p_rec_id);
oci_bind_by_name($stmt,':c_usr_id',$p_usr_id);
oci_bind_by_name($stmt,':c_rslt',$l_results,-1,OCI_B_CURSOR);
if(oci_execute($stmt)){ //Execute the prepared query.
oci_execute($l_results);
while($r = oci_fetch_array($l_results,OCI_ASSOC)) {
$l_evt_values = explode('|', $r['EVENT_VALUES']);
foreach($l_evt_values as $l_evt_value) {
list($l_ID, $l_value) = explode('#', $l_evt_value);
$l_values[] = array('ID' => $l_ID, 'VALUE' => $l_value);
}
$l_result['data'][] = array(
'LOAD_ID' => $r['LOAD_ID'],
'REC_ID' => $r['REC_ID'],
'TRAIT' => $l_values,
'G_MSG' => $r['G_MSG']
);
$l_rslt_msg = $r['G_MSG'];
}
} else {
//echo 'cannot get user';
$l_rslt_msg = '0005'; //PHP_MEMBER.FETCH_USER return error code
}
} else {
//echo 'connect fail';
$l_rslt_msg = '0006'; //Could not connect to database.
}
oci_close($conn);
echo json_encode($l_result);
}
?>
So on a webpage, when a user requests an event, a database call is made using this code to retrieve some values in the format :
"62#20000|65#15710|66#6|67#6|68#0|69#0|".
The PHP then breaks it apart by |, splits the ID#Value, puts everything into an array, then returns it as a JSON which is then parsed into a table. The latter works perfectly fine. But when this tries to fetch more than about 600 records or so, I get a 500 Internal Server Error, and I've figured it's something in this PHP that's handling the call.
I'm not convinced it's the database entirely, as a call for 3500 records with no further processing other than the JSON being returned is generally done in 5s or less.
Why would this code be failing at 500+ records? I've tried AJAX timeout of 0.