Can't make switch from ereg to preg_match work

Question

I have read everything I could find on switching from ereg (deprecated) to preg_match. My attempts to solve it by adding delimiters and escape expressions (which may not be necessary) have been in vain. I started with:

$file = fopen(VARS_FILE,"r");

while(!feof($file)) {
    $line = fgets($file,1000);
    $parts = explode(':',$line);

    if(ereg("breaks",$parts[0]) || ereg("high_",$parts[0]))
        $GLOBALS[$parts[0]] = explode(',',trim($parts[1]));
    else
        $GLOBALS[$parts[0]] = trim($parts[1]);
}

fclose($file);

and tried to change it to:

$file = fopen(VARS_FILE,"r");

while(!feof($file)) {
    $line = fgets($file,1000);
    $parts = explode(':',$line);

    if(preg_match("/breaks/",$parts[0]) || preg_match("/high_/",$parts[0]))
        $GLOBALS[$parts[0]] = explode(',',trim($parts[1]));
    else
        $GLOBALS[$parts[0]] = trim($parts[1]);
}

fclose($file);

This continues resulting in errors like

"fgets() expects parameter 1 to be resource, boolean given in..."

Any advice appreciated.