Evitar ejecuciones múltiples en cron con PHP

¿Para que usar CURL si se puede usar la API de Facebook? sencillo, porque la API no te permite obtener todos los datos que se pueden leer cuando navegas por Facebook. Por ello, en alguna ocasión, nos podemos encontrar con la necesidad de loguearnos en Facebook y “navegar” usando CURL:

echo 'loading 
';
        $login_email = 'my@sexy.mail';
        $login_pass = 'my_sexy_password';

$fp = fopen("fb_cookies.txt", w);
fclose($fp); 

echo 'still loading 
';

if (fb_login($login_email,$login_pass)){
$ch = curl_init();
 curl_setopt($ch, CURLOPT_URL, 'https://login.facebook.com/login.php?login_attempt=1');
 curl_setopt($ch, CURLOPT_POSTFIELDS,'charset_test=%E2%82%AC%2C%C2%B4%2C%E2%82%AC%2C%C2%B4%2C%E6%B0%B4%2C%D0%94%2C%D0%84&locale=en_US&email='.urlencode($login_email).'&pass='.urlencode($login_pass).'&pass_placeholder=&charset_test=%E2%82%AC%2C%C2%B4%2C%E2%82%AC%2C%C2%B4%2C%E6%B0%B4%2C%D0%94%2C%D0%84');
 curl_setopt($ch, CURLOPT_POST, 1);
 curl_setopt($ch, CURLOPT_HEADER, 0);
 curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
 curl_setopt($ch, CURLOPT_COOKIEJAR, str_replace('\\','/',dirname(__FILE__)).'/fb_cookies.txt');
 curl_setopt($ch, CURLOPT_COOKIEFILE, str_replace('\\','/',dirname(__FILE__)).'/fb_cookies.txt');
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.6) Gecko/2009011913 Firefox/3.0.6 (.NET CLR 3.5.30729)");
$html = curl_exec($ch);

 curl_close($ch);

  echo $html;
}


function fb_login($login_email, $login_pass){

 $ch = curl_init();
 curl_setopt($ch, CURLOPT_URL, 'https://login.facebook.com/login.php?login_attempt=1');
 curl_setopt($ch, CURLOPT_POSTFIELDS,'charset_test=%E2%82%AC%2C%C2%B4%2C%E2%82%AC%2C%C2%B4%2C%E6%B0%B4%2C%D0%94%2C%D0%84&locale=en_US&email='.urlencode($login_email).'&pass='.urlencode($login_pass).'&pass_placeholder=&charset_test=%E2%82%AC%2C%C2%B4%2C%E2%82%AC%2C%C2%B4%2C%E6%B0%B4%2C%D0%94%2C%D0%84');
 curl_setopt($ch, CURLOPT_POST, 1);
 curl_setopt($ch, CURLOPT_HEADER, 0);
 curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
 curl_setopt($ch, CURLOPT_COOKIEJAR, str_replace('\\','/',dirname(__FILE__)).'/fb_cookies.txt');
 curl_setopt($ch, CURLOPT_COOKIEFILE, str_replace('\\','/',dirname(__FILE__)).'/fb_cookies.txt');
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.6) Gecko/2009011913 Firefox/3.0.6 (.NET CLR 3.5.30729)");
$html = curl_exec($ch);
 $err = 0;
 $err = curl_errno($ch); 
 curl_close($ch);

 if ($err != 0){
 echo 'error='.$err."\n";
 return(false);
 } else {
 echo 'fetching..';
 return(true);
 }

}

Código fuente en Pastie

Vía / Stack Overflow