php script executes but no output - php

Question

I have gone through all the similar questions and nothing fits the bill.
I am running a big script, which ran on chron on an old server but failed on the new so I am working on and testing in browser.
I have two functions, one pulls properties from the database, and then runs them through another which converts the price into 4 currencies, and if the value is different updates the row. The functions are as follows:
<?php
function convert_price($fore_currency, $aft_currency, $amount)
{
echo "going into convert<br/>";
$url = "http://www.currency.me.uk/remote/ER-ERC-AJAX.php?ConvertFrom=" . $fore_currency .
"&ConvertTo=" . $aft_currency . "&amount=" . $amount;
if (!is_int((int)file_get_contents($url))) {
//echo "Failed on convert<br/>";
return false;
} else {
//echo "Conversion done";
return (int)file_get_contents($url);
}
}
function run_conversion($refno = '', $output = false)
{
global $wpdb;
$currencies = array("GBP", "EUR", "TRY", "USD");
$q = "SELECT * FROM Properties ";
$q .= (!empty($refno)) ? " WHERE Refno='" . $refno . "'" : "";
$rows = $wpdb->get_results($wpdb->prepare($q), ARRAY_A);
$currencies = array("USD", "GBP", "TRY", "EUR");
//$wpdb->show_errors();
echo "in Run Conversion " . "<br/>";
foreach ($rows as $row) {
echo "In ROw <br/>";
foreach ($currencies as $currency) {
if ($currency != $row['Currency'] && $row['Price'] != 0) {
$currfield = $currency . "_Price";
$newprice = convert_price($row['Currency'], $currency, $row['Price']);
echo "Old Price Was " . $row['Price'] . " New Price Is " . $newprice . "<br/>";
if ($newprice) {
if ($row[$currfield] != $newprice) {
$newq = "UPDATE Properties SET DateUpdated = '" . date("Y-m-d h:i:s") . "', " .
$currfield . "=" . $newprice . " WHERE Refno='" . $row['Refno'] . "'";
$newr = $wpdb->query($newq);
if ($output) {
echo $newq . " executed <br/>";
} else {
echo "query failed " . $wpdb->print_error();
}
} else {
if ($output) {
echo "No need to update " . $row['Refno'] . " with " . $newprice . "<br/>";
}
}
} else {
echo "Currency conversion failed";
}
}
}
}
}
?>
I then run the process from a seperate file for the sake of chron like so:
require($_SERVER['DOCUMENT_ROOT'] . "/functions.php"); // page containing functions
run_conversion('',true);
If I limit the mysql query to 100 properties it runs fine and I get all the output in a nice stream. But when I try to run it in full the script completes (I can see from rows updated in db) but no output. I have tried upping the memory allowance but no joy. Any ideas gratefully received. Also, I get a 500 error when changing from Apache Module to CGI. Any ideas on that also well received as ideally I would like to turn site onto fastCGI.

Answer 1

You're running out of memory most likely. Probably in your DB layer. Your best bet is to unset your iterative values at the end of each loop:
foreach ( $rows as $row ) {
...
foreach ( $currencies as $currency ) {
...
unset( $currency, $newr, $currfield, $newprice );
}
unset( $row );
}
This will definitely help.

Answer 2

As another answer suggests you may be running out of memory, but if you make an HTTP call everytime the loop is running, and you have 100+ currencies, this may also cause the problem. Try limit it to 5 currencies for example.
If this is indeed the problem I would split the process, so a chunk of currencies have their respective value updated per cron job, instead of everything.