php - How do I get multiple results from a file opened only once using proc_open? -

i have command run using exec() returns value within large data file, has run millions of times. in order avoid having file opened each time in loop, want move proc_open-based solution, file pointer created once efficiency, can't work out how this.

here exec-based version, works slow, presumably because has open file in each iteration:

foreach ($locations $location) {     $command = "gdallocationinfo -valonly -wgs84 datafile.img {$location['lon']} {$location['lat']}";     echo exec ($command); } 

my attempt @ proc_open-based code follows:

$descriptorspec = array (     0 => array ('pipe', 'r'),  // stdin - pipe child read     1 => array ('pipe', 'w'),  // stdout - pipe child write     // 2 => array ('file', '/tmp/errors.txt', 'a'), // stderr - file write );  $command = "gdallocationinfo -valonly -wgs84 datafile.img"; $fp = proc_open ($command, $descriptorspec, $pipes);  foreach ($locations $location) {     fwrite ($pipes[0], "{$location['lon']} {$location['lat']}\n");     fclose ($pipes[0]);     echo stream_get_contents ($pipes[1]);     fclose ($pipes[1]); }  proc_close ($fp); 

this correctly gets first value, generates error each subsequent iteration:

3.3904595375061   warning: fwrite(): 6 not valid stream resource in file.php on line 11 warning: fclose(): 6 not valid stream resource in file.php on line 12 warning: stream_get_contents(): 7 not valid stream resource in file.php on line 13 warning: fclose(): 7 not valid stream resource in file.php on line 14  warning: fwrite(): 6 not valid stream resource in file.php on line 11 ... 

1. you're not "opening file" you're executing process. if process not designed handle multiple requests within scope of single execution you're not going able around proc_open() or else.

2. in following block you're closing both input , output pipes of process, , yet you're surprised when you're no longer able read or write?

   foreach ($locations $location) {     fwrite ($pipes[0], "{$location['lon']} {$location['lat']}\n");     fclose ($pipes[0]); // here     echo stream_get_contents ($pipes[1]);     fclose ($pipes[1]); // , here } 

   try not doing that.