file

If the file you are reading is in CSV format do not use file(), use fgetcsv().  file() will split the file by each newline that it finds, even newlines that appear within a field (i.e. within quotations).

To write all the lines of the file in other words to read the file line by line you can write the code like this:
<?php
$names=file('name.txt');
// To check the number of lines 
echo count($names).'<br>';
foreach($names as $name)
{
   echo $name.'<br>';
}
?>

this example is so basic to understand how it's working. I hope it will help many beginners.

Regards,
Bingo

this may be obvious, but it took me a while to figure out what I was doing wrong. So I wanted to share. I have a file on my "c:\" drive. How do I file() it? 

Don't forget the backslash is special and you have to "escape" the backslash i.e. "\\":

<?php

$lines = file("C:\\Documents and Settings\\myfile.txt");

foreach($lines as $line)
{
    echo($line);
}

?> 

hope this helps...

read from CSV data (file) into an array with named keys

... with or without 1st row = header (keys) 
(see 4th parameter of function call as  true / false) 

<?php 
// --------------------------------------------------------------

function csv_in_array($url,$delm=";",$encl="\"",$head=false) { 
    
    $csvxrow = file($url);   // ---- csv rows to array ----
    
    $csvxrow[0] = chop($csvxrow[0]); 
    $csvxrow[0] = str_replace($encl,'',$csvxrow[0]); 
    $keydata = explode($delm,$csvxrow[0]); 
    $keynumb = count($keydata); 
    
    if ($head === true) { 
    $anzdata = count($csvxrow); 
    $z=0; 
    for($x=1; $x<$anzdata; $x++) { 
        $csvxrow[$x] = chop($csvxrow[$x]); 
        $csvxrow[$x] = str_replace($encl,'',$csvxrow[$x]); 
        $csv_data[$x] = explode($delm,$csvxrow[$x]); 
        $i=0; 
        foreach($keydata as $key) { 
            $out[$z][$key] = $csv_data[$x][$i]; 
            $i++;
            }    
        $z++;
        }
    }
    else { 
        $i=0;
        foreach($csvxrow as $item) { 
            $item = chop($item); 
            $item = str_replace($encl,'',$item); 
            $csv_data = explode($delm,$item); 
            for ($y=0; $y<$keynumb; $y++) { 
               $out[$i][$y] = $csv_data[$y]; 
            }
        $i++;
        }
    }

return $out; 
}

// --------------------------------------------------------------

?>

fuction call with 4 parameters: 

(1) = the file with CSV data (url / string)
(2) = colum delimiter (e.g: ; or | or , ...)
(3) = values enclosed by (e.g: ' or " or ^ or ...)
(4) = with or without 1st row = head (true/false) 

<?php

// ----- call ------ 
$csvdata = csv_in_array( $yourcsvfile, ";", "\"", true ); 
// ----------------- 

// ----- view ------ 
echo "<pre>\r\n"; 
print_r($csvdata);
echo "</pre>\r\n"; 
// -----------------

?>

PS: also see: http://php.net/manual/de/function.fgetcsv.php to read CSV data into an array
... and other file-handling methods 

^

My experience is that the function file does uses the cached content if the file has changed....

Be aware that using file() to count lines can cause OOM on the server as it'll allocate all lines into an array.

If you're dealing with files that can have thousands of lines, SplFileObject might be a better idea and with little changes you can get the same result.

As of PHP 5.6 the file(), file_get_contents(), and fopen() functions will return false if you are referencing a source URL that doesn't have a valid SSL certificate. Presumably, you will run into this a lot in your development environments this will drive you crazy. 

You will need to create a stream context and provide it as an argument to the various file operations to tell it to ignore invalid SSL credentials. 

$args = array("ssl"=>array("verify_peer"=>false,"verify_peer_name"=>false),"http"=>array('timeout' => 60, 'user_agent' => 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.9) Gecko/20071025 Firefox/3.0.0.1'));

$context = stream_context_create($args);
$httpfile = file($url, false, $context);