filters - Zero-Phase Algorithm in Matlab

From this document it's says

1.Filter the Data

2.Flip that
3.Filter again
4.and Flip that again

for zero-phase filter. but when i do this in matlab , i'm compare between filtfilt method and what i did , it isnt equal. what is the problem ?

MATLAB CODE

clc;clear all;
emg_healthy=load('emg_healthy.txt');
x= 10;
fs= 4000;

my_counter = 1000;
myRawData = emg_healthy(:,2);
myRawData = myRawData(1:my_counter);
myDataRecti = abs(myRawData);
[b,a]= butter(6,x/(fs/2),'low');
filter_y=filtfilt(b,a,myDataRecti);
firstFilter = filter(b,a,myDataRecti);
flip_firstFilter = fliplr(firstFilter);
secondFilter = filter(b,a,flip_firstFilter);
flip_secondFilter = fliplr(secondFilter);

xlabel('Sample Number');ylabel('Genliği');plot(flip_secondFilter,'b');
hold on ;
xlabel('Sample Number');ylabel('Rect Genliği');plot(filter_y,'r');

RESULT

-----------------------------------EDIT-----------------------------------

thanks to robert bristow-johnson, i tried zero-padding to myData , end and begin. This is i try

MATLAB CODE

% % EMG Soleus 

clc;clear all;
emg_healthy=load('emg_healthy.txt');
x= 10;
fs= 4000;
my_counter = 1000;
myRawData = emg_healthy(:,2);
myRawData = myRawData(1:my_counter);
myDataRecti = abs(myRawData);
[b,a]= butter(6,x/(fs/2),'low');
for i = 1:1:(my_counter/4)

myZeroDataRecti(i) = 0;    
end
for i = (my_counter/4+1):1:(my_counter+my_counter/4)
myZeroDataRecti(i) = myDataRecti(i-my_counter/4);
end
for i=(my_counter+my_counter/4+1):1:(my_counter+my_counter/4+my_counter/4)
    myZeroDataRecti(i) = 0;
end
filter_y=filtfilt(b,a,myZeroDataRecti);
firstFilter = filter(b,a,myZeroDataRecti);

flip_firstFilter = fliplr(firstFilter);
secondFilter = filter(b,a,flip_firstFilter);
flip_secondFilter = fliplr(secondFilter);
xlabel('Sample Number');ylabel('Amplitude');plot(myZeroDataRecti,'g');
hold on ;
xlabel('Sample Number');ylabel('Amplitude');plot(flip_secondFilter,'b');
xlabel('Sample Number');ylabel('Amplitude');plot(filter_y,'r');
% 

RESULT

another i try , i again add zero-padding begin and end but i used filtfit method to apply without zero-padding data

MATLAB CODE

% % EMG Soleus 
clc;clear all;
emg_healthy=load('emg_healthy.txt');
x= 10;
fs= 4000;
my_counter = 1000;
myRawData = emg_healthy(:,2);

myRawData = myRawData(1:my_counter);
myDataRecti = abs(myRawData);

[b,a]= butter(6,x/(fs/2),'low');
filter_y=filtfilt(b,a,myDataRecti);
for i = 1:1:(my_counter/4)
myZeroDataRecti(i) = 0;    
end
for i = (my_counter/4+1):1:(my_counter+my_counter/4)
myZeroDataRecti(i) = myDataRecti(i-my_counter/4);

end
for i=(my_counter+my_counter/4+1):1:(my_counter+my_counter/4+my_counter/4)
    myZeroDataRecti(i) = 0;
end
firstFilter = filter(b,a,myZeroDataRecti);
flip_firstFilter = fliplr(firstFilter);
secondFilter = filter(b,a,flip_firstFilter);
flip_secondFilter = fliplr(secondFilter);
xlabel('Sample Number');ylabel('Amplitude');plot(flip_secondFilter,'b');
hold on ;

xlabel('Sample Number');ylabel('Amplitude');plot(myDataRecti,'g');
xlabel('Sample Number');ylabel('Amplitude');plot(myZeroDataRecti,'c');
xlabel('Sample Number');ylabel('Amplitude');plot(filter_y,'r');
% 

RESULT

in my opion, there are two things we have to think about that,

1.First picture in the edit part,my signal (myCode-LEGEND) amortize itself , but matlab function (filtfilt) keep continiues , why is that ?

2.Second picture in the edit part, my signal(myCode-LEGEND) different from filtfilt function signal. And between myCode and 250Zero+originalData+250Zero i think it doesnt any phase shift. If we say that it's true what should i do ? Will i remove 250 zero from begin and end ?