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Is there way to append data to file on specific line or something similar like that?

I have an "handmade" array in my file, and I need to keep my beginning and end of the array.

I would like to have something like this:

$array = [
    *create new line and write data here*,
*previous data*,
*previous data*,
*previous data*,
];

EDIT: I currently only know how to append data at the end of the file, and I haven't found proper solution. If I append my data with just file_put_contents();, it won't be in the array:

$array = [
    *previous data*,
    *previous data*,
    *previous data*,
    ];
*create new line and write data here*,

EDIT: I got my answer. There is no efficient way to do this.

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5
  • What research have you already done? What is the code you have currently? What is not working with your current approach? Please read MVCE. Commented Oct 27, 2017 at 14:31
  • not sure I understand your question, but you can use array_unshift() to prepend elements into your existing array. Commented Oct 27, 2017 at 14:34
  • I have "handmade" array in one separate file and I want to write data to that file, but it needs to go between the array tags. Sorry, if my explanation is bad Commented Oct 27, 2017 at 14:40
  • So, you want to change the code of the separate file? Commented Oct 27, 2017 at 14:46
  • Basically yes. Add data with file_put_contents(); , but I need it to append on specific line, not at the end of file. Commented Oct 27, 2017 at 14:49

3 Answers 3

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You can't add a line in a middle of a file. You need to rewrite the file with something like this (not memory expensive) :

// Read your old file
$read = fopen('myfile', 'r');
// Create a new file
$write = fopen('myfile.tmp', 'w');

while (!feof($read)) {
  $line = fgets($read);
  if (stristr($line, '$arr = [')) { // For your case
    $line .= "YOUR NEW LINE\n";
  }
  fputs($write, $line);
}

fclose($read);
fclose($write);
// Rename the new file
rename('myfile.tmp', 'myfile');
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If writing to a file, there are not many (any, in my personal experience!) options for efficient prepending or mid-file inserts. Almost all of the working world relies on appending to files. You can do it, but only through basically rewriting the entire file. In essence, you have to "move all the other lines down", and that takes work.

If this is something you need done efficiently, consider a more appropriate data structure. Perhaps multiple arrays (e.g., perhaps in reverse order), multiple files, a sorting key for after load sorting, etc. But you are not likely to get around the issue of slow performance when prepending or inserting to on-disk files. (And if you do, likely involving some kernel editing, then consider making some money or helping the FOSS world out!)

If you are doing this in memory, then the data structures and access patterns are much more robust, and so you can do operations like array_unshift:

$arr = [
  "line 1",
  "line 2",
  "line ..."
];

array_unshift($arr, "line 0");
# $arr is now: [
#  "line 0",
#  "line 1",
#  "line 2",
#  "line ..."
#];
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Well then. As simple as it seems, it's not easy to do. Thank You for replying and explaining this for me.
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To add elements at the beginning of an array use array_unshift:

$a=array ("content of a line", "another line");
array_unshift($a, "content to be added");

print_r($a); //print out to check

'array_push' does the same but add element(s) at the end of the array

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