How to output (to a log) a multi-level array in a format that is human-readable?

Question

I'm working on a drupal site and when debugging, I am always having to read through long, nested arrays. As a result, a large portion of my life is spent using the arrow, return, and tab keys, to split up 1000+ character strings into a nested, readable format.

For drupal devs, I can't use devel's dsm(), as I'm working with multi-step #ahah/#ajax forms, and I can only output the arrays to the error log, not to the screen.

Visual example:

Evil:

array ( 'form_wrapper' => array ( '#tree' => true, '#type' => 'fieldset', '#prefix' => '', '#suffix' => '', '#value' => '', 'name' => array ( '#type' => 'textfield', '#title' => NULL, '#size' => 60, '#maxlength' => 60, '#required' => false, '#description' => NULL, '#attributes' => array ( 'placeholder' => 'Email', ), '#post' => array ( 'form_wrapper' => array ( 'name' => '', 'pass' => '', ),

...

Good:

array ( 
'form_wrapper' => array ( 
    '#tree' => true, 
    '#type' => 'fieldset', 
    '#prefix' => '<div>', 
    '#suffix' => '</div>', 
    '#value' => '', 
    'name' => array ( 
        '#type' => 'textfield', 
        '#title' => NULL, 
        '#size' => 60, 
        '#maxlength' => 60, 
        '#required' => false, 
        '#description' => NULL, 
        '#attributes' => array ( 
            'placeholder' => 'Email', 
        ),

Edit: Sorry, by "not output to screen", I meant via drupal's system messages where it's possible to output arrays in a clickable, nested format (using devel.module).

1

'.print_r($array,1).''; ?> – Rufinus Aug 09 '12 at 13:53

score 256 · Accepted Answer · edited Mar 02 '23 at 06:40

256

If you need to log an error to Apache error log you can try this:

error_log( print_r($multidimensionalarray, true) );

If you would like to capture the output of print_r(), use the return parameter. When this parameter is set to true, print_r() will return the information rather than print it.

edited Mar 02 '23 at 06:40

Avatar

14,622
9
119
198

answered Sep 11 '13 at 12:48

Akhilraj N S

9,049
5
36
42

3

Looks like it's `print_r` (lowercase). Does `print_R` really work as well? – evanrmurphy Jul 29 '16 at 21:13
thanks @AkhilrajNS can you tell me more about how can i send the inserted query or any query which is executed above this log message.? – always-a-learner Jan 19 '17 at 03:52
@ankitsuthar Did you mean SQL Query ? – Akhilraj N S Feb 10 '17 at 05:27
Yes But I got it by the last query function in CI. Actually, I want to log a data which are get inserted or edited, deleted. – always-a-learner Feb 10 '17 at 05:56
This is dum. This outputs newline characters as literal `\n` instead of actual newlines. – Otheus Oct 24 '18 at 10:09
@Otheus I think may have missed the point in the first sentence. This targets the APACHE ERROR LOG which is a single entry per line. If you want to capture multi-line info it needs to be escaped. – oligofren Jan 07 '22 at 14:46
@oligofren perhaps I missed Akhillaraj's point, but the OP asked for something _human readable_. Apparently this is an apache "security" fix: https://stackoverflow.com/a/1574558/3849157. But the idea of `print_r` is to output the array in a human-readable way and apache kills that. His is the top answer, mysteriously. Well, maybe things changed since 2013. Or maybe he uses php-fpm or CGI. – Otheus Feb 23 '22 at 11:54

Fivell · Answer 2 · 2012-08-09T14:16:06.127

23

http://php.net/manual/en/function.print-r.php This function can be used to format output,

$output = print_r($array,1);

$output is a string variable, it can be logged like every other string. In pure php you can use trigger_error

Ex. trigger_error($output);

http://php.net/manual/en/function.trigger-error.php

if you need to format it also in html, you can use <pre> tag

edited Aug 09 '12 at 14:16

answered Aug 09 '12 at 13:54

Fivell

11,829
3
61
99

1

Read the question - OP needs to do this for log output - not screen output. – Matt Aug 09 '12 at 13:55
@Matt read the answer, `if you need to format it also in html` – code-jaff Aug 09 '12 at 14:08
@Fivell, I try. If you clarify your answer to explain that the output can be sent to the log file, I'll remove my -1. – Matt Aug 09 '12 at 14:11
1

@Fivell there's a small issue with `trigger_error` it limits messages to max 1024 length or something similar. Making some longer `var_exports`/`print_r` strings get cut-off. It's useful for simple structures. – Mihai Stancu Aug 09 '12 at 14:19

wittich · Answer 3 · 2022-12-13T00:12:42.680

I just wonder why nobody uses or recommends the way I prefer to debug an array:

error_log(json_encode($array));

Next to my browser I tail my server log in the console eg.

tail -f /var/log/apache2/error.log

Though it's debatable if the output is human-readable, but it's still my preferred way to read it and would look something like that:

[Tue Dec 13] [...] AH01071: Got error 'PHP message: {"form_wrapper":{"#tree":true,
"#type":"fieldset","#prefix":"","#suffix":"","#value":"","name":{"#type":
"textfield","#title":null,"#size":60,"#maxlength":60,"#required":false,
"#description":null,"#attributes":{"placeholder":"Email"},"#post":{
`"form_wrapper":{"name":"","pass":""}}}}}', referer: http://localhost/

Because it's not "human readable" :D Seriously, this is a good idea though. A post-processor combined with `jq` can make this an excellent debugging tool — Otheus, Feb 23 '22 at 11:55

Mihai Stancu · Answer 4 · 2012-08-09T13:59:43.890

Simple stuff:

Using print_r, var_dump or var_export should do it pretty nicely if you look at the result in view-source mode not in HTML mode or as @Joel Larson said if you wrap everything in a <pre> tag.

print_r is best for readability but it doesn't print null/false values.

var_dump is best for checking types of values and lengths and null/false values.

var_export is simmilar to var_dump but it can be used to get the dumped string.

The format returned by any of these is indented correctly in the source code and var_export can be used for logging since it can be used to return the dumped string.

Advanced stuff:

Use the xdebug plug-in for PHP this prints var_dumps as HTML formatted strings not as raw dump format and also allows you to supply a custom function you want to use for formatting.

Read the answer `var_export` allows you to return a string. – Mihai Stancu Aug 09 '12 at 13:58 — Mihai Stancu, Aug 09 '12 at 13:58

nmc · Answer 5 · 2012-08-09T14:13:55.253

Drupal's Devel module has other useful functions including ones that can print formatted arrays and objects to log files. See the guide at http://ratatosk.net/drupal/tutorials/debugging-drupal.html

dd()

Logs any variable to a file named “drupal_debug.txt” in the site’s temp directory. All output from this function is appended to the log file, making it easy to see how the contents of a variable change as you modify your code.

If you’re using Mac OS X you can use the Logging Console to monitor the contents of the log file.

If you’re using a flavor of Linux you can use the command “tail -f drupal_debug.txt” to watch the data being logged to the file.

score 1 · Answer 6 · edited Aug 09 '12 at 14:17

1

This will help you

~~echo '<pre>';~~

$output = print_r($array,1);

~~echo '</pre>';~~

EDIT

using echo '<pre>'; is useless, but var_export($var); will do the thing which you are expecting.

edited Aug 09 '12 at 14:17

Mihai Stancu

15,848
2
33
51

answered Aug 09 '12 at 13:56

code-jaff

9,230
4
35
56

1

@Matt When this parameter is set to TRUE, print_r() will return the information rather than print it. – code-jaff Aug 09 '12 at 14:01

score 1 · Answer 7 · answered Nov 13 '20 at 09:38

Syntax

print_r(variable, return);

variable Required. Specifies the variable to return information about

return Optional. When set to true, this function will return the information (not print it). Default is false

Example

error_log( print_r(<array Variable>, TRUE) );

Joel Larson · Answer 8 · 2012-08-09T14:03:35.810

0

~~You should be able to use a var_dump() within a pre tag. Otherwise you could look into using a library like dump_r.php: https://github.com/leeoniya/dump_r.php~~

My solution is incorrect. OP was looking for a solution formatted with spaces to store in a log file.

A solution might be to use output buffering with var_dump, then str_replace() all the tabs with spaces to format it in the log file.

edited Aug 09 '12 at 14:03

answered Aug 09 '12 at 13:51

Joel Larson

3,064
1
15
12

Read the question - OP needs to do this for log output - not screen output. – Matt Aug 09 '12 at 13:55
I did read the question. Missed that last little comment. Thanks for letting me know. This solution is not going to work then. – Joel Larson Aug 09 '12 at 13:59

How to output (to a log) a multi-level array in a format that is human-readable?

8 Answers8

Simple stuff:

Advanced stuff: