I have this function in PHP, it runs a Python code that returns the temperature coming from the Arduino.
I need it to run every 2 seconds so I can display the updated information on the browser screen.
What would be the best way to do this?
function retornaTemperatura()
{
$comando = escapeshellcmd('temperatura.py');// Local do arquivo python
return shell_exec($comando);// retorna o valor do py para exibir ou mandar para um banco de dados
}
Web is something that will always have the complete answer, if you use sleep you will have problems, headaches, especially if you have session_start , understand that I am not saying that sleep is bad, the use of the way proposed in the other answers is not ideal.
I think it's best to use Ajax and popular a DIV, for example:
foo / temperatura.php
<?php
function retornaTemperatura()
{
// Local do arquivo python
$comando = escapeshellcmd('temperatura.py');
// retorna o valor do py para exibir ou mandar para um banco de dados
return shell_exec($comando);
}
echo retornaTemperatura();
And on your page call something like this:
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body>
<div id="temperatura"></div>
<script type="text/javascript">
function temperatura()
{
var el = document.getElementById("temperatura");
var segundos = 2; //2 segundos de espera
var oReq = new XMLHttpRequest();
//Defina como true
oReq.open("GET", "/foo/temperatura.php", true);
//Função assíncrona que aguarda a resposta
oReq.onreadystatechange = function()
{
if (oReq.readyState == 4) {
if (oReq.status == 200) {
el.innerHTML = oReq.responseText;
}
setTimeout(temperatura, segundos * 1000);
}
};
//Envia a requisição, mas a resposta fica sendo aguardada em Background
oReq.send(null);
}
</script>
</body>
</html>
Note: Since I did not give more details about running the function, I declined to show an example of how to repeat execution in PHP only, as if it were a script language to execute directly on the operating system (not the web). I will not answer the second case, since the @GuilhermeNascimento is complete and will answer you.
You will have to call the function multiple times, waiting a certain amount of time with each call.
For this, you can use the sleep function, it receives as a parameter the number of seconds the script will wait until it continues the implementation.
while(true){
$valor = retornaTemperatura();
sleep(2);
}
You can do this:
while(true) {
retornaTemperatura();
sleep(2);
}
The best way to do this is to create a task scheduler to run your script every 2 seconds. To do this, it will depend on which server is windows or linux, and a certain configuration in apache.
For Linux server:
crontab -e
2/* * * * * /usr/local/bin/php /usr/var/www/seu_script.php
For windows you can follow this example .
However, if this script will run only when run (once), you can do something like this:
function retornaTemperatura()
{
$comando = escapeshellcmd('temperatura.py');// Local do arquivo python
echo shell_exec($comando);
}
while (true) {
try {
retornaTemperatura();
} catch (Exception $e) {
echo "<meta http-equiv='refresh'" .
"content='2;url=" . $_SERVER['SCRIPT_NAME'] . "'>";
}
sleep(2); // aguarda 2 segundos
}
or if you want to limit the number of executions you can do so
$num_max=10;
$delay=1; // 1 segundo de pausa entre cada execução
for($i=1;$i<=$num_max;$i++){
retornaTemperatura();
sleep($delay);
}
So you control how many times it will run and how long you wait.