How to check for value in a PHP array?

Question

When I enter the page PHP already has an error:

Notice: Undefined index: name in C: wamp www index.php on line 41

Here is the code:

include ("conexao.php");

$nome = $_POST["nome"];

$resul = mysql_query("SELECT * FROM funcionarios WHERE nome = '$nome'");

while($row = mysql_fetch_array($resul))
{
print "
<tr align='center'>
<td> $row[id_funcionario] </td>
<td> $row[nome] </td>
<td> $row[idade] </td>
<td> $row[sobrenome] </td>
<td> $row[senha] </td>
</tr>
";

}

Checking for value in a PHP array?

Answer 1

You can use the isset to check if the variable has been set. Thus, you will only show the information that the nome be informed:

include ("conexao.php");

if(isset($_POST["nome"]))
{
   $nome = $_POST["nome"];

   // NÃO USE mysql_query! 
   // Risco de SQL Injection.
   // Pesquise por mysqli e\ou PDO.
   $resul = mysql_query("SELECT * FROM funcionarios WHERE nome = '$nome'");

   while($row = mysql_fetch_array($resul))
   {
      print "
      <tr align='center'>
      <td> $row[id_funcionario] </td>
      <td> $row[nome] </td>
      <td> $row[idade] </td>
      <td> $row[sobrenome] </td>
      <td> $row[senha] </td>
      </tr>";
   }
}

Answer 2

The isset has a problem, it informs only if the variable was started, in your case if the variable is set to empty '' the code will be executed. I recommend using !empty, which in turn checks whether the variable is not empty.

if( !empty($_POST["nome"]) )
{
    // código
}

Answer 3

On the line where:

$nome = $_POST["nome"];

You can modify to:

$nome = isset($_POST["nome"]) ? $_POST["nome"] : '';

This way will avoid the code error, but with or without POST request it will perform the query in the database, if you prefer to perform query only when there is the POST request, use the @Lucasnunes example.

Answer 4

Although much has been suggested to the use of isset() I suggest you prefer array_key_exists() instead.

That’s because isset() with arrays besides checking if I determine the index exists will also check its content. And this is where the danger lies because, in certain circumstances, such as validation algorithms, it can be interesting to have indexes present but empty.

And a check with isset() can end up damaging logic and even hindering a debugging.

Notwithstanding, isset() also requires more processing than array_key_exists() precisely because two distinct tests are made distinct for the same simple purpose.

Of course, this falls into the category of micro optimizations that is not the focus here and should only be taken into account in Applications medium-large fully developed with isset().