如何在PHP中的字符串之间拆分？

I have the following string in a text file:

^b^B

I'm trying to split this into two variables. My current code is using explode() but it does not work as I want it to:

$num1 = '^b';
$num2 = '^B';

How can I accomplish this using PHP?

THIS IS MY CODE

<?php 
if(isset($_POST['refresh'])) {
exec('/var/www/www.rfteste.com/htdocs/estado.sh');
}
if(isset($_POST['on'])) {
exec('/var/www/www.rfteste.com/htdocs/on.sh');
}
if(isset($_POST['off'])) {
exec('/var/www/www.rfteste.com/htdocs/off.sh');
}
echo "<H3>CONTROL PANEL</H3>";
$str = file_get_contents("/var/www/www.rfteste.com/htdocs/refresh.txt");
$vals = explode("^", $str);
$num1 = "^".$vals[0];
$num2 = "^".$vals[1];
$onoff= "^A";
if($num2 == $onoff)
echo "<b>on</b>";
else
echo "<b>off</b>";
?>
<html>
<body>
<form method="post" action="">
<p>
<center><input type="submit" value="on" name="on""';" /></center>
<center><input type="submit" value="off" name="off""';" /></center>
<center><input type="submit" value="refresh" name="refresh""';" /></center>

Use preg_split() with a lookaround assertion:

list($num1, $num2) = preg_split('/(?<=\^b)/', $str);

Autopsy:

/ - starting delimiter
(?<= - start of positive lookbehind (meaning "if preceded by")
- \^b - match literal characters ^b
) - end of positive lookbehind
/ - ending delimiter

Visualization:

enter image description here

In plain english, it means: split on places where it's preceded by a ^b and assign the array values to the variables $num1 and $num2 using the list construct.

Demo

Use preg_match_all():

<?php
$str = '^b^B';
preg_match_all('/(\^.)/', $str, $matches);

var_dump($matches);

#Pull all of the contents of file, myfile.txt, into variable, $str
$str = file_get_contents("myfile.txt");

#split up the data in $str, at every instance of '^'. 
$vals = explode("^", $str);
#now $vals is an array of strings

#concatenate the "^" back into the strings as they were removed by explode.
$num1 = "^".$vals[0];
$num2 = "^".$vals[1];