Works for me on OSX just fine:

for ($i = 1.0; $i >= 0; $i -=  0.05)
{
        print "my i value is '$i'\n";
}
print "end of script\n";

please post a full sample script if this continues.

Reopened this bug. My understanding of this that it counts to (inclusive) 0.:

Extendet the script like this:

<?php
for ($i = 1.0; $i >= 0; $i -=  0.05)
{
        print "my i value is '$i'\n";
}
print "end of script\n";

for ($i = 10; $i >= 0; $i -= 1)
{
        print "my i value is '$i'\n";
}
print "end of script\n";
?>

the result is:

bndiap56> php4-200207301200_install_alpha_tru64/bin/php php-bugs/18682.php
Unaligned access pid=146367 <php> va=0x14005e3ec pc=0x1201c6910 ra=0x1201c6904 inst=0xb4010000
my i value is '1'
my i value is '0.95'
my i value is '0.9'
my i value is '0.85'
my i value is '0.8'
my i value is '0.75'
my i value is '0.7'
my i value is '0.65'
my i value is '0.6'
my i value is '0.55'
my i value is '0.5'
my i value is '0.45'
my i value is '0.4'
my i value is '0.35'
my i value is '0.3'
my i value is '0.25'
my i value is '0.2'
my i value is '0.15'
my i value is '0.1'
my i value is '0.05'
end of script
my i value is '10'
my i value is '9'
my i value is '8'
my i value is '7'
my i value is '6'
my i value is '5'
my i value is '4'
my i value is '3'
my i value is '2'
my i value is '1'
my i value is '0'
end of script

never compare floats for equality. period.
see http://php.net/float or your favourite
computer science book for why not to do so