Take a specific part of a string

Question

I need to take a specific part of a log file, its structure is something like this:

##################################################
----------------------------------------
Nome: nome_user,
Email: [email protected],
-------------------------------
,
----------------------------------------
##################################################

Let’s say I need to take only value country Email, how can I do this?

Answer 1

You can do it in a very simple way:

$start = 'Email:';
$end = ',';

$pos1 = strpos( $log, $start );
$pos2 = strpos( $log, $end, $pos1 );
$block = substr(
   $log, $pos1 + strlen( $start ),
   $pos2 - $pos1 - strlen( $start )
);

See working on IDEONE.

Of course, for the specific case it is possible to write in a much more summarized way:

$pos1 = strpos( $log, 'Email:' );
$pos2 = strpos( $log, ',', $pos1 );
$block = substr( $log, $pos1 + 6, $pos2 - $pos1 - 6 );

If you need to test cases where there is no field Email: in the log:

$pos1 = strpos( $log, $start );
if( $pos1 === false ) die( 'Campo não encontrado' ); // ou return ''; se usar em função.
...

Creating a function:

In general, you can have a function to extract the data you want. There are a thousand ways to do it, this is one of them:

function my_extract( $text, $start, $end ) {
    $pos1 = strpos( $text, $start );
    if( false === $pos1 ) return 'Não encontrado';
    $pos1 += strlen( $start );
    $pos2 = strpos( $text, $end, $pos1 );
    return trim( substr( $text, $pos1, $pos2 - $pos1 ) );
}

Mode of use:

$nome  = my_extract( $log, 'Nome:' , ',' );
$email = my_extract( $log, 'Email:', ',' );

See demonstration on IDEONE.

Using cannon to kill dove:

Since fatally someone would end up posting, follows a solution with Regex:

if( preg_match( '/Email:\s*(.*)\s*,/', $log, $matches ) ) {
    $email = $matches[1];
} else {
    $email = ''; // Não encontrado
}
// podia ser um operador ternário, mas não é o foco da pergunta,
// não ajuda na leitura do código e não ajuda na performance.

Again, see working on IDEONE.

If only to find an occurrence of string, do not recommend. It seems simple, but internally the function does a lot more than you need for the proposed problem.

Description of the regular expression:

 /                 /    delimitadores
  Email:                string procurada
        \s*    \s*      espaços em branco
           (.*)         grupo que queremos retornar (quaisquer caracteres)
                  ,     marcador do final

Extra considerations:

• If you want to use accentuated strings in the future, such as "Profession:", and the encoding of your text is multibyte (as UTF-8) for example, instead of strpos use mb_strpos and configure your PHP for encoding correct.

• As mentioned by fellow @lvcs, in case you have any situation where you want to locate both Email as EMAIL or eMaIl, can change the strpos for stripos, or the mb_strpos for mb_stripos

• In case you want to insensitive search with Regex, you have to add the flag i at the end of the expression (add a i after the last bar).

• If you really want to ensure that the string Email: not be confused with something in the middle of the line, can specify "$Email:" as a marker to include the line break in the query, and the flag m for multiline research.