Hi I´m new in php and in one book i found this:
$x = 0;
if ($x-- == 0) echo $x;
in book they write it should write -1 to my page, because decremenet was done after comparison and before the command exho was executed. I understand why it is that, but when I type it into my editor it's giving me error because it's understanding $x-- as one and $x as another variable. Where's problem?
Basic Steps :
Step 1: (get Notepad++)
Go to http://notepad-plus-plus.org/ and download Notepad++.
Notepad++ is a free (as in "free speech" and also as in "free beer") source code editor and Notepad replacement that supports several languages. Running in the MS Windows environment, its use is governed by GPL License.
Step 2: (type the code)
type and save as "filename.php" in "www directory"
<?php
$x = 0;
if ($x-- == 0) echo $x;
?>
Step 3: (enJoy !)
Check the result
Expected Output :
-1 // this is what i got! :D
$x-- is postdecrement that is the $x value will be still 0. when you went away from the statement then only the $x value should be change. so if statement is working fine. the echo value will be -1.
7-isnotbad answer is correct.
Related
This is a strange bug I've come across when switching my code over from 000webhost to ipage. It's the same code and a consistently different result.
The following example does nothing.
echo 0;
This example gives us '00'
echo 0;
echo 0;
Seems to be a problem with ipage's host. This is my current workaround. This workaround echoes 00 instead of 0, and the correct integer with no leading 0 otherwise.
if(empty($count[0])) echo 0; // Don't get why we need this--not needed on 000webhost, e.g.
echo $count[0];
Update: confirmed bug on ipage's end
For a command line application I am trying to ask a simple question using the following code (example is not real life, code, but resembles the "real" version):
echo "Do you want to quit? [Y]/N";
$handle = fopen ( "php://stdin", "r" );
$input = trim(fgets($handle));
if ( empty($input) ) {
$input = 'Y';
echo "Y\n";
}
The result I want, is the following - When a user does -NOT- provide input:
Do you want to quit? [Y]/N: N // User only hits enter, not 'N'..
What I get is:
Do you want to quit? [Y]/N: // User only hits enter, not 'N'..
N
So the question is: How do I force echo 'Something'; to NOT print a newline after the echo.
Basically I need the equivalent of bash's echo -n '...' (does not print the trailing newline).
To understand why is it so - you need to understand that there are two things: STDIN and STDOUT that are involved into program. And - yes, php does not add new lines. With simple echo "foo"; you'll get exactly "foo", without new line.
But why are you seeing new line then? Simple: because you've pressed "it". That is: you've pressed "enter" key, terminal got it and printed it. Your program, of course, also got it, but at that moment the "key" is already printed.
What can you do? On that step: nothing. It's already done and that's it. You'll see it in your screen. However, yes, there is a trick that I can suggest. You can use stty to maintain behavior, when you can control the input and/or output. Combined with system() you'll get the idea.
Here we are with code:
function emulatePrintable()
{
$result = '';
while($c = trim(fgetc(STDIN)))
{
echo($c);
$result.=$c;
}
return $result;
}
system('stty -echo');
echo("Do you want to quit? [Y]/N ");
$result = emulatePrintable();
if($result==='')
{
echo("You didn't type anything!");
}
echo "\n"; //<--- this is to delimit program's end of work
system('stty echo');
What's happening? You're doing this:
Suppress any input printing with stty -echo. This is the trick. You're suppressing only input display, not output display. That is why you'll be able to see echo() strings from PHP
Emulating output for printable characters. That is: you still want to show what user is typing (your Y or N) - but you want to skip new line. Simple emulatePrintable() will do the work (may be not the best name, but at least I've tried)
After you've got the input (it's interrupted with EOL, for example) - you can examine what is it. If it's an empty string, then you've caught it: user typed nothing.
Now, do not forget to enable input display with stty echo - otherwise.. well, you'll end with "non-working" terminal.
Benefit: with this you'll be able even to decide, to print character or not (for example, to restrict only Y and N for output).
So this is the solution for unix-based OS. In Win - best of luck to you. You may check this page for console modes & related stuff, but I'm not sure it will work (since have not tested).
i've got this snazzy python code:
import subprocess
value = subprocess.Popen(["php","./php/php_runner.php"],stdout=subprocess.PIPE);
the problem is, i have no idea how to check if the php_runner, well, ran. Currently, it has the following salient sections:
if (count($argv) != 4){
die("four arguments are needed\n");
}
and
$returnValue = call_to_another_php_class();
return $returnValue;
So what i want is this:
How do i get the return value, whatever it may be, using python?
You probably are going to tell me to use "PIPE" in the answer, but the (to me, incomprehensible) python docs (http://docs.python.org/library/subprocess.html) state:
Do not use stdout=PIPE or stderr=PIPE with this function. As the pipes are not being read in >the current process, the child process may block if it generates enough output to a pipe to fill up >the OS pipe buffer.
So what do i use then, because while I don't really know what they're barking on about, i sit up and take note about notes in grey boxes. Pity they didn't spell out what i'm meant to do - but, well, what am i meant to do?
the "returnValue" that my php code returns, is that what python is going to pickup as the return value from the function? If not, how do i return that value?
cheers!
UPDATE
Thanks to the given answer, here's the changes i made:
edited /etc/php5/cli/conf.d/mcrypt.ini (actually, this is just a change for ubuntu 10.04, and I changed the first line to begin with a ; instead of a #. That stopped an annoying "we don't like #" error that kept popping up)
in my php, I changed the code to read:
if (count($argv) != 4){
fwrite(STDERR, "four arguments are needed\n");
exit(1); // A response code other than 0 is a failure
}
this puts my error value as an error. the die() command wasn't doing that for me.
changed the python to read:
value = subprocess.Popen(["php","./php/php_runner.php"],stdout=subprocess.PIPE,
stderr=subprocess.PIPE);
print value.communicate();
Yeah, realistically, i'd do an if on value.communicate()[1], becase that is where the errors are.
$returnValue = call_to_another_php_class();
if ($returnValue == 1){ //hah, php has a good return value as 1.
//no problem
} else {
fwrite(STDERR,get_error_from_php_class());
exit(1);
}
booyah!
Since you're using the Popen constructor rather than the call functions, those notes about PIPE don't apply to you.
Use .communicate() as documented to wait for the program to finish and get the output.
I relogin to my server in dreamhost and test some scripts.And I found I couldn't use str_split. Message of Undefined function was given.I checked the version in the server and its PHP Version is 5.2.12.And I just wonder which version is required?Thanks.
Testcode:
<?php
$arr = str_split("lsdjflsdjflsdjflsdjfl");
print_r($arr);
?>
Message:
Fatal error: Call to undefined function: str_split() in /test.php on line 3
Edit #Justin Johnson
I checked the server's system directory,and I found there are two versions of PHP in Dreamhost.In user's webroot,file will be parsed by PHP5 and that's why I got php 5.2.12 by putting a phpinfo.php in the webroot.And if php files are ran in command line directly using php test.php,another php version which is 4.x worked.That's the reason I got an error.When I use
/usr/local/php5/bin/php test.php
Everything is fine.
Rather than use str_split, it's usually much easier to iterate through the characters of the string directly:
$s="abc";
$i=0;
while(isset($s[$i])) {
echo $s[$i++]." ";
}
see?
First off: The PHP documentation will always say what version is required for every function on that function's documentation page directly under the function name.
It is possible that an .htaccess file is somewhere in your path and is causing a previous version (<5) of PHP to be used. To double (or triple) check to make sure that you are running in the proper PHP version, place this code above the line where you call str_split
echo "version:", phpversion(),
"<br/>\nstr_split exists? ",
function_exists("str_split") ? "true" : "false";
However, as shown by Col. Shrapnel, it is not necessary to convert a string to an array of individual characters in order to iterate over the characters of that string. Strings can also be iterated over using traditional iteration methods, thus making the call to str_split unnecessary and wasteful (unless you need to segment the string into fixed length chunks, e.g.: str_split($s, 3))
foreach ( str_split($s) as $c ) {
// do something with character $c
}
can be replaced by
$s = "lsdjflsdjflsdjflsdjfl";
for ( $i=0; isset($s[$i]); ++$i ) {
// do something with character $s[$i]." ";
}
which is equally, if not more clear.
According to dreamhost wiki, you need to switch to php5 manually from control panel, if you created your domain before 2008 sept.
http://wiki.dreamhost.com/Installing_PHP5#Using_DreamHost.27s_PHP_5
PHP 5 was added to all plans by
DreamHost as of June 2005. As of
September 2008, support for PHP4 was
discontinued, so you can no longer
switch back to PHP 4 from PHP 5 from
the panel.
If you haven't switched to PHP 5 yet,
you can do this in the Control Panel.
But, again, you will not be able to
switch back to PHP 4 after switching
to PHP 5.
Here's how to switch from PHP 4 to PHP
5:
Log into the DreamHost Control Panel.
Click Domains, then Manage Domains.
Click the wrench icon next to the domain you want to activate PHP 5
on (under the Web Hosting column).
Select PHP 5.x.x from the dropdown menu.
Click Change fully hosted settings now! at the bottom of the
section.
Repeat steps 3-5 for each additional domain you want to
activate.
you could also check your php version with
<?php
phpinfo();
?>
The version required is PHP 5 or later. So theoretically your program should work.
If you can't get str_split to work, just use a string as an array:
$stuff = "abcdefghijkl";
echo $stuff[3];
will produce
d
This method is fastest, anyway. I don't know if it suits your needs, but if it does, I hope it helps!
Could be anything in your code. How do we know its not a 10 line script or 2000 line script?
You can use preg_split() to split an array into single characters, but it will return an extra empty string at the begining and the end.
$a = preg_split("//","abcdefg");
echo json_encode($a);
prints:
["","a","b","c","d","e","f","g",""]
I have a php script that is running in CLI and I want to display the current percent progress so I was wondering if it is possible to update the STDOUT to display the new percent.
When I use rewind() or fseek() it just throws an error message.
See this code:
<?php
echo "1";
echo chr(8);
echo "2";
The output is only 2 since "chr(8)" is the char for "backspace".
So just print the amount of chars you need to go back and print the new percentage.
Printing "\r" works too on Linux and Windows but isn't going to cut it on a mac
Working example:
echo "Done: ";
$string = "";
for($i = 0; $i < 100; ++$i) {
echo str_repeat(chr(8), strlen($string));
$string = $i."%";
echo $string;
sleep(1);
}
Output \r and then flush to get back to the first column of the current line.
Writing to a console/terminal is surprisingly complex if you want to move backwards in the output raster or do things like add colours - and the behaviour will vary depending on the type of console/terminal you are using. A long time ago some people came up with the idea of building an abstract representation of a terminal and writing to that.
See this article for details of how to do that in PHP.