How would you explain to someone that there are…

Semantic errors are related to the fact that the code is formally correct (no syntactic errors), but its execution behaves unexpectedly or not as intended. This can be a logical error, incorrect API usage, data type mismatches, business logic errors, etc.

Examples of semantic errors in PHP:

Incorrect condition logic:

// It is assumed that if the number is less than 0 OR greater than 100, there will be an error.
// But due to a logic error, the condition will never be true.
if ($number < 0 && $number > 100) {
    echo "Error: number out of range.";
}

Using a variable before initialization (although PHP may silently treat it as null/0):

// $uninitialized_var_before was not declared
$sum = $uninitialized_var_before + 10; // May lead to unexpected results
echo $sum;

Type mismatch in operations:

// Comparing strings and numbers can lead to unexpected results
$str = "10php";
$num = 10;
if ($str == $num) { // The == operator performs type juggling
    echo "They are equal (unexpected).";
}

Incorrect API function usage:

// Intended to delete a file, but the function expects a file path, not an object
$file_object = new SplFileInfo('/path/to/file.txt');
unlink($file_object); // Error: unlink expects a string, not a SplFileInfo object

Logical errors in algorithms:

// Error in loop or calculations leading to incorrect results
$total = 0;
for ($i = 0; $i <= 10; $i++) {
    $total += $i; // This sums from 0 to 10
}
// If the intention was to sum only numbers from 1 to 10, there is a semantic error.

Fixing semantic errors requires understanding the intended behavior of the code, thorough testing, debugging (using debuggers, logs, var_dump), and analysis of business logic.

How would you explain to someone that there are semantic errors in their code?