Data commit

Task/Undefined-values/PHP/undefined-values.php

@@ -0,0 +1,33 @@
+<?php
+// Check to see whether it is defined
+if (!isset($var))
+    echo "var is undefined at first check\n";
+
+// Give it a value
+$var = "Chocolate";
+
+// Check to see whether it is defined after we gave it the
+// value "Chocolate"
+if (!isset($var))
+    echo "var is undefined at second check\n";
+
+// Give the variable an undefined value.
+unset($var);
+
+// Check to see whether it is defined after we've explicitly
+// given it an undefined value.
+if (!isset($var))
+    echo "var is undefined at third check\n";
+
+// Give the variable a value of 42
+$var = 42;
+
+// Check to see whether the it is defined after we've given it
+// the value 42.
+if (!isset($var))
+    echo "var is undefined at fourth check\n";
+
+// Because most of the output is conditional, this serves as
+// a clear indicator that the program has run to completion.
+echo "Done\n";
+?>